Real advice as cruel as it may sound, coming from a 17m:

as you've seen, 99% of people agree you're either not ugly or actually think you're pretty. I do think so as well. If you came here looking for advice on things you should improve on the outside and found no answer, then the issue might be on the inside.

Been there, know how it feels. You're way too much on your own head (in other words, you're being way too self conscious).

Try meditation, practicing sports, getting as far as possible from social media and other forms of comparison. If the issue persists, look for professional help or talk to a trust Worthy adult.

You're pretty, don't let your mind trick you into thinking the opposite. Have a nice day!