I don't understand people or attraction. No one has ever been attracted to me but my husband, as far as I know.

However, when I go for an intense swim, I can see that my face looks fantastic afterwards and the next day also. I pee a gallon afterwards (sorry for TMI) so I think all the pumping moves fluids out of the body. Less puffy looking. Accounts for nicer looking face, in part. I'm not thin, either, by far. Maybe you'd like to try swimming. It can feel good, too.

The sex thing might not be about you. Your bf is also getting older and probably more stressed, I would guess. Anyway, people's desires change over time. Have you talked with him about it?