Agreed. I’d much rather my mom ask a question here than share details of my sex life with her friends.
And speaking on intimate details, it might be a good idea to talk with your son about the emotional responsibilities of intimacy. My sense is that most young people get decent guidance on the health issues (although use of condoms bears repeating), but that there may be less discussion and preparation for the emotional and social issues. No means no (even when it was yes yesterday), don’t discuss your sex life with others and be careful what you put on social media, physical intimacy can create emotional vulnerability, etc. Basically, there’s more to be careful with than good BC can protect you from.
Well, sometimes anonymity is helpful.
As to the issue at hand, great that he let you know. Talk to him as an adult : about what sex means to him, what it can create even with BC, if they discussed how an unexpected pregnancy would be handled. Open communication with a double dose of responsibility. I remember feeling confident with BC as a young adult; by the time I was 35, I knew many sophisticated people with unplanned pregnancies, several with health issues that precluded carrying a baby. They were very careful, yet…
The horse is out; it will likely stay out. But conversations over time may gradually help him think about the bigger picture. Yes, as a parent ignorance can feel like bliss, but only temporarily. Perhaps being a sounding board since he lives in the house is an opportunity. Also, have lots of people with young, fussy babies visit and enlist his help in tending them while you visit with parent/s. Just kidding, sort of…
DD had a hall mate who started her freshman year of college pregnant. She kept the baby, planned to take a semester off, but wound up living with her mother and attending another college part time, locally. She finished college only a year later than expected. Father was uninvolved. Super bright, wanted med school. Not practical to pursue that yet. She is 26 with an 8 year old. This stuff is real.
Best to all
Maybe the dad, if he doesn’t have a CC acct can create one and provide responses.
Condoms. Condoms, condoms, condoms.
Sex has always been very openly discussed in my house and I still didn’t tell my parents when I started having sex. (Dad figured it out by finding a condom receipt.) It was sometime around sophomore year and by that time, I was over the age of consent (definitely check this!). I had been on birth control since I was in my young teens but was still adamant about using condoms every time. Make sure both parties know that the typical use failure rate for condoms and oral birth control are higher than most people expect. If she is using an IUD or implant, kudos! But I say as an HIV counselor: I cannot tell you how many young people come to me wanting an HIV/STI test because they “made a mistake” at a party or something and their bf/gf “absolutely cannot know.”
So again: condoms. condoms. condoms.
And you or his father or someone else he is willing to discuss it with might want to make sure he knows how to use condoms correctly/properly.
^ Yes. You’d be amazed at how many people I have to teach how to put on a condom at my university.
(I’m not going to lie though- it is one of the more fun parts of my volunteer work. Almost always, the guys will turn bright red when I pull out a dildo to show them how to put on a condom properly.)
What happened to the bananas - or do you just enjoy watching them blush? 
I wish I could say I planned this… but I am given a dildo, not bananas.
I have no control over any of the objects at my disposal in the counseling room. 
I think you should be proud that your S told you. That means he fells comfortable with you.
I also highly agree with gardenstategal # 21. Talks need to be had about the emotional responsibilities, and responses of intamicy.
I actually strongly advocated to my kids to remain virgins, until they graduated HS. And I am pretty sure they all did. Of course any # of other sexual acts may have been indulgeged in. Haha And people define virgins differently.
My main reason for this hope or request was the emotional aspect. Teens are so vulnerable and affected by peers. They need to learn, at this stage, who they are and what they want and not gets snapped up in even more emotions that control them.
Besides condoms to reduce the risk of pregnancy and STDs and checking age of consent laws, check on their HPV vaccine status. HPV is an STD that can cause cancer (both female and male).
Sounds like the horse is being put in the barn, regularly…
When I was in high school I had the decency to not burden my parents with the details of my sex life.
Why would I have wanted to put that knowledge on them?
The thought of the kids having sex in the house makes me less squeamish than the kids having sex in my car.
^Cloth or leather seats?
I wouldn’t want to have sex in a car, where strangers could walk up to the window and watch and where I would have no opportunity to clean up afterwards.
Why should a young couple have to?
When I had my first relationship with a guy, which started the summer before college and continued during breaks from college (we were at different schools), we had sex in my home or his, usually but not always when our parents were elsewhere.
When my son had his first relationship with a girl, which happened while they were still in high school, they had sex at our home, usually but not always when my husband and I were elsewhere.
The world didn’t come to an end in either case.
My kids have sex in my home. Big whoop. Seems like a natural thing to do in a loving relationship at some point. I’ve never heard them or been aware of when it was going on, just like my spouse and I keep our own intimacy on the down low. Not that hard to do. Not sure why folks think it’s going to be so obvious.
There’s some chance that if kids are caught in a car, they could be charged with some sort of crime. Not terribly likely but not impossible.
As far as I know my kids never had sex my home while they were in high school. Neither had a serious local BF/GF for very long. But if they did, the house has survived it.
They could also be victims of some sort of crime.
Having sex in the house is not really that big a deal. Most parents don’t get home from work until late afternoon or early evening. Most high school kids get home much earlier. Much teenage sex takes place in the afternoon for just that reason. All you need to do is make sure your kid knows when you won’t be following your usual schedule. A quick “I’ll be home early tomorrow because someone’s coming to fix the dishwasher” ought to do it.
OP I don’t think you have too much to worry about. Seems like your S is in a steady, healthy relationship and has been very up front about it. The birth control issue appears to be covered and the GF’s mother is also aware of how the relationship has progressed. In contrast to the “hook up” culture that is so pervasive today, it appears your S has chosen a different path- he should be applauded in my opinion.
I don’t know how I feel about the sex in the house thing. Guess I would take the easy way out and think “fine so long as I am not home at the time.” I somehow can’t get comfortable with one of my high school aged children having that explicit license while others are in the home. But that’s just me…
I had 2 serious boyfriends during my college years and often went to their homes during the summer or on holidays. Although both relationships had progressed to sexual intimacy, I made it clear to both of them that I would not be staying in the same room while at their parent’s home. I was very concerned about what the family would think and I just felt it was “crossing a line.” My parents never let us share a bedroom in our home, so it was what I was used to. One BF was perfectly on board with that but the other fought me on it all the time - he eventually got the “heave-ho.”
It actually is a very big deal to a great many people, for a variety of reasons. I probably fall on the more liberal side of this discussion, but I understand that there a lot of legitimate chains of thought on the subject.