I'm a 17 year old boy, in my final year of sixth form preparing to go to university... but I have a problem, which I feel is progressively getting worse.
In recent years I know I've become more anxious around other people my age, and not only has this severely affected the social side of my life, it's starting to affect the academic side too (that is, from the constant worry and anticipation of forced social interactions, such as lunch break).
Strangely, this anxiety appears to be situation-dependent. For example, in my physics class I sit with a small group of (and I hate to use this term) fairly "popular" boys from my year, and without a single butterfly in my stomach I can communicate with them, laugh, joke, and relax. I really value these lessons because in any other time of the day things couldn't be worse.

The sixth form life at my high school involves many parties, relationships, and socialising... but I have become very detached, but not out of choice. Almost all students spend breaks and lunch in the "common room", a large room with a few tables and chairs - sixth form only. This probably sounds ridiculous, but as of yet I've not used it - I can't. Walking past the door sends butterflies through my system, sometimes I even panic. I can hardly bring myself to look in as I walk past. I don't really know why I behave like this, but I know I fear rejection unlike anything else. I even fear rejection for being one of the few NOT to use the common room, and I make it my business at lunch time to keep myself on the move. I don't want people to see me stand alone, so I make frequent trips to the toilet (if only to waste time in a cubicle), or I just sit near people I hardly know, just so I don't look "friendless".
But "friendless" is possibly a word to describe the situation - I haven't been out with friends for what feels like years, and I cannot bring myself to attend parties - I am terrified of rejection that could happen.
Deep down I know this view on rejection is a warped few on the reality around me. I know deep down that the chances of rejection and criticism are very low - and this hurts. If I know this deep down - then why can't I act appropiately? It feels like I'm losing control of a part of my personality, and this frightens me.
Sex is inevitably becoming a part of the lives of my peers, and I worry about some bizarre thoughts I've had related to the subject. Sometimes I start telling myself that intimate love and intercourse are evils - I have essentially found myself rejecting the concepts entirely if in the frame of mind. Sometimes I even find myself desiring a life of solidarity. Why? I don't know, because deep down like any other human I desire companionship and love, but that fear of rejection is twisting me, and I feel like I'm losing control of myself.
I don't get any chances to initiate relationships (and if I did I know I would avoid them), because I always have an excuse not to attend a social event. Take today as an example. Two lads from that physics group (who in the classroom situation I can talk to free of butterflies) invited me somewhere afterschool, and at that moment the butterflies hit. Was it the prospect of being with other people in a new situation? I don't know, but I didn't like the feeling and made an excuse to get out of it.
I'm so sorry for the long post, and probably the oddness of it all. I read about AvPD, and I really connected with the topics in the article. It hit home to me that I have a problem which could ruin my life if I don't confront it. I can't tell my family because I'm ashamed, which is why I'm opening up here.
If there is any advice, anything at all that can help me avert ruining my life at university and beyond, please help me. I read that joining a gym is good way of confronting this problem, and I am seriously considering this. I have a burning desire to lead the "normal" social life of a person my age, but something in me is stopping me. I want to overcome it so badly, but maybe I'm weak. Maybe I just have to throw myself into the deepend.
Any replies appreciated. Thanks.
