okay i would first like to say that the best idea is to talk to a therapist, they may not work how you want but later on YOU yourself figure out the problem because they open your eyes to something you dismissed
ok what you have i am not sure the name at all, CAN turn into an eating disorder so please do not take this issue as being just a fear. it is okay to be fat, as long as you can carry out every day activities. you need to start believing it yourself, not just saying it to be okay. also i would like to add it is better to be fat than have anorexia or bulimia, as long as your gaining wait just cuz you dont eat the healthiest of things. also you need to talk to people, like friends and family. they might see things about you that you overlooked that maybe the cause maybe when you were fat people made fun of you, making a phobia out of weight.
the last thing is never ever if you are called fat believe them, only you can judge what is fat to you and NO being a beam pole is not "perfect"
if you need more help pm me