Yes, I do believe you have an eating disorder. Eating disorders often go beyond just image, they're deeper than that. Laxatives shouldn't be used to to lose weight, that's dangerous! I strongly suggest telling a trusted adult about your problem before it progresses any further! I used to have bulimia when I was about 13 years old, and it's not fun. I was always on a "pedastool" to seem perfect to my parents. I learned after keeping my secret in for so long that my life wasn't worth being "skinny." It's about being healthy, that's all that really matters. Why don't you just start exercising with your friends? Like play a sport or something to keep your mind off of your disorder.
Not only will it make you become healthier, you will also be so busy that you'll begin to forget all about your disorder.