My best advice is listen to him! He thinks you're beautiful and he cares about you I have some body image issues and I had a therapist who kept telling me to "fake it, till you make it." Yes, intellectually you probably know better than to listen to external validation to boost your self esteem. But perhaps instead of working to convince yourself you're right and your body is a problem, why not work on convincing yourself that he's right and you are beautiful?

I also had a doctor who had me write a positive mantra about myself every time I wrote in my journal which was daily something to the extent of I love myself for me and write down one good thing about myself each time. Hopefully something different but even the same thing. I found that helped a lot too.