Social problems began at the age of three, when I first went to daycare. I cried the whole time I was there on the first day, and was taunted by the other kids because of it. I also didn't really understand how other children worked and they would often avoid me or criticize me for not reaching certain developmental milestones.
Things only became worse in elementary as I became more cognizant of my rejection. I was called a retard, had rocks thrown at me, and was made the but of jokes.
Didn't realize at the time that everyone else was going through normal puberty and I was the weird one.
That is exactly how I felt in junior high. I did not think highly of my peers to begin with, but suddenly they seemed to become exponentially stupider. All of the guys would make disgusting sexual jokes on a constant basis and lace their language with profanity for no apparent reason, conflict and drama proliferated, and most of the students seemed more interested in gossip than actually learning anything. I figured I was just in a particularly bad school, or that there was some unknown factor effecting their behavior. It turns out it was just teenage hormones, the same hormones my body was subject to, and yet I didn't have the same response.
In high school I never dated, didn't really party, and could count my friends on one hand. It was around this time I discovered I was physically incapable of approaching people and trying to make friends.
Despite all of that, I preferred junior high to elementary, and high school to elementary. In my early 20s, when I entered the queer community, my social prospects suddenly blossomed and I found myself able to connect with new people in a way I didn't know was possible. For me, the question wasn't so much when my problems started as when they started to let up. I think it was a combination of life experience, other peoples maturity, and learning to self-select my peer group to include people who accept my differences.