My high school days are very much in my past.
Looking back, I can see that I was avoidant then, but I didn't realize it. Getting worse and recognizing it is what makes me now see I was avoidant then.
I'm not sure what to say to motivate you so you can escape the problem. I think there were about 2000 students at my school. I still live in the same metropolitan area. I have occasionally encountered someone from my graduating class (of course many when I went to a reunion, but elsewhere too) and I find they don't recognize me or my name as having been at school with them at all. I made zero impression. The few people I socialized with at school don't go to the reunions and I never see them.
So, if you can muster up the courage to make yourself participate, I would recommend it. Join some of the non-dorky clubs, try out for the less competitive sports teams, be in band or chorus, and volunteer to do things at school. In each thing you can get yourself to try, pick one person to be your "friend" for that activity and try to interact with that person. Just asking the same person what's happening, or what you missed, or what to do, could be your excuse to interact.
I didn't do that, of course, so I don't know that it will help. It's just what I now think I should have done then.