How to tell someone you’re not physically attracted to them?

I love my boyfriend, I do. But I’m not physically attracted to him. He’s on the heavier side but it’s not the weight that just turns me off it’s the fact that he just doesn’t take care of himself. I mean he showers and all that but down there still smells and idk, I’m just all around turned off and I’m just not interested in sex. And he’s always in the mood. How should I break it to him?

Update: I feel like I should add some more background. My boyfriend and I have been together for a year and a half and at first I kinda just dismissed this turned off feeling but then it got worse. His area didn’t always smell, but it is kinda small and unfortunately sex is not always the best. And I just don’t know how to tel him all this