He makes me feel bad

My fiancé and I have been together 3.5 years and we got pregnant after just a month of dating so our sex life hasn’t been the greatest he’s a big man so he can’t do positions I like and so we only have sex with me on top well the last year has felt like he doesn’t find me attractive anymore he would rather masturbate then to have physical relations with me I’ve tried talking to him about it but all it get from him is “so what’s the problem” what do I do now ?