My insecurities about my body

My fiance like a to look at my body when im naked. I hate it though. Im a little heavy and I don't feel comfortable when he just stares at me. In bigger than he is and it always makes me feel disgusting. I always feel like the "fat one." I hate when he wants to take my bra off and just let my boobs sit there all bare and with no cover. He just stares at me and i can't help but feel that he's thinking "why did I get with this whale?" I know he must love me for wanting to eventually marry me, but I always question why is he even with me when I don't stand a chance against other girls he could have.