I was quite brash as a child, a high achiever in school and sports, so i had a pretty healthy ego distracting me. Now i look back on it, the symptoms were pretty much always there. I was never in the "in" crowd, and had a few best friends but mostly acquaintances.
I never had to do many speeches in class, although i remember feeling 'funny' whenever i did. I couldn't really understand it, cos i was always quite confident. But I really began to notice that I had a problem on the transition to high school.
The few friends i had went to different high schools, I was all alone! I walked around the schoool grounds during recess and lunch time, watching all the kids making new friends and playing, feeling very alone and depressed.
Thankfully this lasted only a few weeks, when i was suddenly yanked out and sent to a selective high school after a position opened up there. On my first day, one of the kids there "took me under his wing" and helped me integrate into a group of good people.
Finding a GF there, I fell madly in love, which delayed me again noticing that i had a problem. It wasn't until about year 10 or 11, when i started smoking pot, that it came to the fore. I remember the exact time aswell, i'd been smoking the whole weekend and I remember being at school the following monday and feeling very different. My brashness turned to anxiousness, and people noticed. My sheltered little cocoon was smashed.
My GF and i drifted apart and i slipped further into the alcohol and drug culture to the point where I was injecting heroin. It took years to finally break out and realise i had to stop. Its been a few years since i've touched anything but the SP has still persisted.
P.S that was very cathartic, my thanks to the orginal poster!