I learned the hard way. I even changed schools because I couldn't deal with those constant comments about me. It's not easy to get over this, however, you should trust yourself and be confident in what you think is best. If someone talks bad about you, just let it pass your ears as if it never entered. It will always hurt, but in the end you should know that they just do that because they want to better themselves and found something about you which they do not have and because of that, they try to make themselves look better. If you understand what I mean? Anyway, my point is, that as long as you do not give rude comments about others, you are not hurting anyone and therefore you cannot/should not get hurt. If they do it anyway, ignore it, find someone you feel confident around and act as if nothing ever happened. What also helps, is if you are nice to them because they will be positively surprised