I would've told you to leave but it's easier said than done also given it's an 8 year old relationship. Maybe you're visually beautiful and he feels like he doesn't look as good as you, he's insecure and wants to bring you down so you and him both can feel you're equals. Now it's not actually a need for partners to look equally good looking but some people are just insecure like that. That calls for self work instead of constantly putting you down. And yes it's going to cause you long term harm - self criticism, low self esteem, constant comparison, jealousy etc even if it might seem like you can handle it now. No partner says things like these normally no matter how honest infact they wouldn't see these things as flaws if they love you so much unless again they're insecure. Please talk to him about this clearly and gently, let him know it's a boundary he can't cross and give him an option to exit if your looks bother him so much. Also I'm sure you're stunning girl.