@student5436, what kinds of activities/ECs did you do at home? Let us know, and maybe we can help you brainstorm. Also, what are some activities you always wanted to do/learn, but never had the opportunity to do? Getting involved will help break the ice.
Great comments here…just want to add: do your best to not be intimidated by your roommate’s friends coming over. This is very important because you’re establishing the dynamic in your relationship early on; you don’t want to let that feeling of being overpowered get entrenched.
You don’t have to be good friends with your roomate or her friends, but if they come over, you have every right to be wherever you want on your side. If you really dislike anyone sitting on your bed, make that clear to your roommate when her friends aren’t there but don’t sound angry (or too meek), just matter-of fact. Or, as @Empireapple said, if it’s commonly done and you can learn to be OK with it, just make sure you’re not pushed out. Just say, casually, with as much good humor as you can muster, something like “hey…scoot over” or, “you get the chair, I get the bed :)” or, “Umm, I need some room here.” Do it as if it’s not a big deal, but never forget that you’re entitled to your own room. Maybe go bake some cookies and pass them around to break the ice.
Do you get any exercise?Make sure you’re getting enough! Taking a run every day, swimming laps or working out in the gym can help ward off depression with an exercise “high”, help you sleep better and make you feel more confident in your own skin. That, in turn sends positive messages to others. A pro-active person is always going to attract others to you more than someone who feels defeated and gives off that vibe. (You might find a workout friend that way, too).
Others here are right! You don’t have to be an extrovert to get involved. You were able to make and keep good friends in high school. You can do this. It’s scary to take the first steps, but do something every day.