Not dating because of size.

Now I'm a small guy, only 5 11 130. I was pretty into this girl, she's only like 5 6 but is much heavier than me. It didn't bother me to much, but as things started to get more serious and she was starting to really get into me I started seeing some things. She had gained a lot of wait between high school and college, and her older sister the same, and she was now much heavier yet. I feel like a fuck for it, but I just don't see myself in a relationship with someone like that or bigger 5-10 years down the road. Just looking for thoughts on my situation.