Bulimia. why did i get fat again?

I was bulimic this time last year. I was really small now I'm stopping it. Well I have stopped it. Right before I got on birthcontrol. I eat better and I don't purge. (Throw up) but I've gotten soo fat. I've gained at least 25 pounds and I don want to slip back into being bulimic. What can I do? I've been exercising too. Nothing is working so I'm afraid I might go back to what I know from fear of being fat. I weigh 160 and 5'1 I used 2 weigh 140. But all the weight was in my boobs and butt. So I looked very curvy which I liked. Now I'm just getting fat. Any advice. I don't want to purge anymore?