Family thinks I have an eating disorder

So, I am a small girl. I am only 5'1 and about 105 lbs. I seriously don't eat a LOT, it's very very rare when I do. I do not have literally any issues with my body, the thought of an eating disorder has NEVER crossed my mind. It doesn't take much to make me full. My entire family and boyfriends family thinks I lie when I say I am full. It is unbelievable how many times I say NO, I do not have an eating disorder. It's kind of to the point where I feel offended by it. I don't look that skinny at all, in fact for my height you can see chub on my stomach. Has anyone else ever dealt with this? I find it incredibly frustrating and don't know how I am supposed to make people believe me. I do NOT have an eating disorder.