School was the worst experience in my entire life and I too have a lot of built up resentment and anger. It got so bad at one point I found a lot of the bullies on facebook and messaged them if they had regrets about the way they were at school. All but one never replied and blocked me, which to me implied they were ashamed and wanted to pretend nothing happened. Some of them have kids now which scares me because a lot of them (the girls) were physically abusive. I have extreme social anxiety and get panic attacks in large crowds or even just walking through town.
The one who did reply apologised and for me that helped provide a little bit of closure. I'm not saying you should stalk these people or anything lol but maybe if you get the chance ask them why. You are a better person than they will ever be and the fact you've managed to survive this far proves that. Try not to let it eat away at you too much because its not healthy, I know! Hang in there!