feelin unwanted

I'm 21 weeks pregnant, my relationship is wonderful but i sometimes feel that thing between me and my finace have changed since i've gotten pregnant.We don't have sex like we use to and i feel it's maybe because im gaining weight, He say's im sexy as hell but i sure don't feel sexy i feel fat and blah looking because i have stretch marks on my belly,legs,butt, and my boobs. Maybe it's normal for my to feel this way and it'll get better as my belly and baby get bigger. i just wonder if anyone else feels this way to.