SUBREDDIT: r/relationships
TITLE: I [21 F] have been avoiding certain sex positions with my boyfriend [24 M] due to my size.
POST: I'm in a fairly new relationship with a really great guy, we've been seeing each other for about 3 months and everything between us is great. 

Recently though he's been wanting me to get on top during sex WHICH I honestly would love BUT I'm a larger girl, about a size 16, and I've always been self-concious about my weight and how it would feel for him. So I've been putting it off. People have told me that I wouldn't crush him or anything but I guess I don't have the reassurance I need and I feel like if I did get on top I would be too much or it wouldn't feel good and be super uncomfortable for him. I know i would just be constantly worrying about it. He tells me that he would love it if I got on top as well which makes me feel worse. 

Am I being irrational? Has anyone else had this problem with their partners, male or female? Any tips/tricks?I would love some imput!
TL;DR: 
I'm a size 16 and I'm worried I'll turn off my boyfriend during sex on top due to my weight. Should this be something I should worry about?