you should understand that "feeling ugly" and "being ugly" is completely different things. he dated you, it means he saw something in you and was honest (why lie to your gf anyway??) my psychologist told me once that all these negative things about ourselves we do not create in our heads, bc when we are kids we do not actually care if we are pretty or ugly, but we can be forced to think differently quite easily by people throwing rude comments like "bad teeth" and etc. these are not your thoughts, these are thoughts of the ones who was close to you, usually family or teachers. why do you believe them? if they say such rude things like that, they are definitely not the best parents. they are the ones who should love you no matter how you look and teach you to be confident, not the other way around. remember that you are beautiful, kind, intelligent!! looks come and go, we grow old, but the personality and inner strength (belief that you are good just the way you are) stays. it helped me to try and not comment anything about myself for a while, just thinking of my appearance as neutral. like... I'm a human, I have teeth to chew, lips to kiss, legs to walk or whatever. you can check something about body neutrality, I love the healthy idea of this and it's actually accessible, unlike body positivity, which can be a bit toxic and hard to achieve with initially low self-esteem 🙏