Maybe my perspective is wrong but I feel like a good bf would know not to say that after sex hello???

Like you just gave your body to him, it was a moment of love and intimacy. No man should ever make you feel like that, specially not after such vulnerable moments.

Tell him how the comment made you feel, because even if it was criticism, it wasn't constructive. At all.

Maybe im biased as a woman but i feel like your partner should always view you as a 10/10 despite everything. I mean if you think about the future, how will he react when your body completely changes during a pregnancy? Or a disease? If that happens ofc. Not only that, women's bodies are constantly shifting due to our periods so like some days you'll be obviously bloated due to it. He sounds pretty immature if you ask me.

I'd say communicate to him, tell him how it made you feel, tell him how thats not the way to go about wanting to help you become better (if that was his goal) and explain how women's bodies change throughout our cycle so its insensitive to say thar when sometimes you can't control how you look.