Well here is the prolem if they like you they won't find you ugly. If they find you ugly they dont like you.
What he/she wants is sex, that is all. They would obviously prefer it with someone else that wasnt "ugly", but something is better than nothing. Now if all you want is sex then there is no problem. If you are sure that is all you want, most people tend to fool themselves on this point. If you want more, than you are just asking for that huge barn door of pain to go smashing at your heart like a blacksmiths hammer on an anvil.
It is up to individuals to decide. I'm not a prude and don't care if people have sex with each other for any reason at all. However having lived long enough and experienced enough, I can state emphatically that sex with someone you love is infinitely better than with someone you care nothing for.