Ironically, its 4:33 a.m. as I post this
But I only do it once a week for a standing early morning meeting and it kicks my butt!
These are just thoughts, RM - trust I am personally no good at this at this moment in time
I just happen to have two clients that work in this field, one of whom trains and manages a large triathlete team and a second who gets outstanding results on a mere total hour a week circuit training.
First off, for the kind of strength training that requires a gym, you can (and generally should) only be going 2-3 times a week max or you will overtrain. And it shouldn’t take more than a half hour/40 min. to do the circuit. But your resistance exercises should increase weight wise every time you go so that you get maximum exertion/burn. Otherwise, you’re just kinda wearing out your joints. And you should take a full day of recovery, sometime two.
In a past life, I’ve done this kind of circuit training, with a coach, and its just true. Two mornings a week and a casual weekend trip is just easier to manage and ultimately more effective. More effective because your body actually needs that recovery time to rebuild the micro muscle tears and burn off the lactic acids released. Your metabolism from this kind of circuit will stay well elevated 24 hrs or more after, which supports diet efforts as well because your resting metabolic rate will be increased.
On off days, if you want, you can get a lot of benefit without overtraining by doing something like a lunch hour spin, run, or Nordic walking (walking with ski poles that doubles the burn and works the traverse muscles.)
As to why you feel so tired, I actually think its either your body TELLING you to knock it back a bit, or that perhaps your nutrition isn’t dialed in. The body gets cranky if the caloric intake is less than the (now elevated) resting metabolic rate – and you actually lose more if you’ve matched up your nutrition and your metabolic rate. This is where lots of people stall.
Some trainers have machines to test your metabolic rate and max vo2 rate during exertion and work up a program that’s most efficient based on this pretty customized approach. If you want to sleep more but make the kinds of gains you have in strength and weightloss, its worth looking into because you can truly do more with less if its all dialed in… The point of exercise at all is to give you more energy…not take it 
You can’t out-train your diet, but they say you can make the two work together efficiently.
Now, this is hilarious coming from me so I’m going to go get another coffee and crawl into the hot tub and look up at the stars…which is how I deal with 4:30 am days 