Hey, I can relate. I'm in my 20s as well.

I pretty much can't seem to make or keep friends too. It's like when you open up, they run away...and if you don't open up, you lose friends.

I work in an office, so it's different from University but maybe you might be able to do something similar. I try to "act friendly" when I'm going to different places in the office -- smile even when I don't feel like it, say "Hi" and wave to people I recognise even when it feels really weird.

Some people have told me I seem more "happy and cheerful" and they smile when they see me or greet me first. It's usually when meeting in corridors or a few minutes just before a meeting.

Maybe we will stop to talk a little bit about nothing important. "How are you?" "Nice weather, huh"...stuff like that. I don't enjoy it and I find it tiring but I do it to seem friendly and if I focus on them, I come across as less unfriendly and anxious.