how to become less sensitive?

I would put this in the category of self improvement but there is none for questions. how do i become less sensitive? Is that even possible or is it a personality trait that can not be changed? I'm definitely not in the worst situation in my life, but i have had a few events in life that made me really sensitive over certain topics in mot sensitive until it comes to these topics. I am sensitive over biking accidents and injuries that cause your body to look ugly, parenting (too laid back), being bullied, and immigration. i was in a biking accident as a kid which stunted my growth in my leg because it hit the epiphysial plate in one leg. so now my leg is a inch shorter then the other. I am an immigrant and i had many people in my life who were against immigrants and really dislike them. my mom was too laid back and what i would call a free range parent when i was younger, she let me ride on busy roads when i was a kid and a car crashed into me when i was riding down a hill on a bike.the car ended up stopping so just my leg got injured. I was bullied for being in English as a second language parents teachers and most of my classmates called me stupid and the kid's would talk slow and pretend i was stupid. I stayed in English as a second language until eleventh grade. i asked to go into higher classes and they said i was not going to be able to handle them because im not at the mental level the other kids were at both my parents and teachers said this, and the reason i was not at the level is because my elementary school and up to sixth grade they took me out of all classes to put im in esl all day. i did not pay attention in esl and hated English. I did end up catching up in highschool and now im in college getting a bachalors degree but i have very low self esteem from that and still i chose a bad college because i thought i was too stupid for any other colleges, and still wonder if im good enough for a harder college. please help me.