What is wrong with me?

Ok, im 18 years old and a pretty good looking guy... I see many chicks and i can get them to like me really fast and during that time im really interested in them but as soon as they like me i loose all interest in them. I don't know why i do it my friends say im too picky but it i don't think that is the case.. also i get repulsed by little things. What should i do? also small things bug the crap out of me like for instance this one girl she was y as hell so i took her to dinner and she chewed really weird and i stoped talking to her because of it is that bad of me ?