@Aya dh ,
People fall for all different types of other people. My son is thin and his fiancee probably outweighs him by 80 pounds. Does not seem to bother my son in the least. Nor should it. He loves the person.
Your boyfriend might be the same weigh. He cares for you. The whole person, not just the packaging you currently come in. Be happy he is not superficial. And if it bothers you that much, change your eating habits/life style with the goal of losing some weight. But really, unless your weight is causing you health issues, if you are happy and he is happy, what is the problem?
(Note: I am not suggesting you make any life-style changes for anyone other than yourself. Changing to simply make someone else happy is not a good pattern for a relationship.)