Do I have an eating disorder? My mom and friends are worried about me...?

I wouldn't say you have one. As long as you're eating your doing good but you should be a bit concerned about how your thinking. This could possibly and slowly lead into anerexia(I can't spell it :( ) and in case it does you should do what ever you can to prevent yourself from getting it. Just do things like activites that get your mind off your weight, honestly for a girl your height that's not too much to worry about. Being skinny doesn't have a lot of perks. If you can't find a way to stop thinking about calories and weight then ask your mom if you can go to a counsler or a therapist to help you.