Your text could describe myself. I am in worse condition because I am older.
This time I am writing this I am sad because of that certain lifelong problem. Today a friend messaged me and asked me if I'd like to go out with 'them'. I said 'sure but who else is gonna come along?' Wanna know? It's gonna be him, his friends and his girlfriends. What am I gonna bring together? My cat? I don't think I am gonna go now.
Lately I made a small step. I found something that I always wanted to do in my life. I got to the gym to practice martial arts. (I always secretly wanted to try martial arts). It's not that I have friends now but I HAVE to talk and have contact with people. It's something isn't it?
I will give you some advices that work sometimes with me. When you are with other people. DO NOT THINK ABOUT YOURSELF. Let yourself free, say what you wanna say. Let things carry on naturally. Think less and act more.
You are still young. Smile. Make as much friends you can and eventually get a girlfriend.