There are many different signs that your partner is not physically attracted to you.I can answer this from the other side. Before my gf and I broke up I stopped being physically attracted to her even though I still loved her and thought she was objectively an attractive person.
She did nothing wrong and I still felt a lot of affection, the sexual attraction just wasn’t there. So what happened is that we would kiss, but I wouldn’t want to french kiss, so it would just be lips pressed on lips. I liked it because I loved her, but the thought of tongue wrestling started to repulse me.
I stopped wanting sex as much and would sometimes lie my way out of it, or have to pretend she was someone else in order to get off. It’s awful and I felt terrible about it, and she deserves better, and I hope she gets it.
It’s not like I wanted to not feel sexual attraction and it didn’t start that way. I tried to get back to that place and just couldn’t. I treated her like a queen in other ways to try and make up for it while I figured the attraction part out, but in the end it wasn’t fair to her and I’m happy she’ll get a chance to meet someone who can lust for her how she deserves.
So all in all, as per the OP, it was not wanting sex as much, but the thing I most remember is not wanting to tongue kiss anymore. That was the smoking gun.