Advice for my relationship?

So i have been with my partner for 7 years now and were set to get married next year. I love him so much. but, were only 20 and recently ive put on some weight and i just dont feel very atractive and happy with how i look. For a while now i just dont feel like having sex but obviously does and i dont know what to do, i cant help the way i feel i just dont feel in that kind of mood anymore. we have aa duaghter together so she takes up alot of my time and by the time i finish work and done the things i need to do i just dont feel like it. Ive been feeling like this for a couple of months now. Before it was often then its just got less and less then once a week now its not even that What can i do?