Theres a possibility that you have messed up your metabolism from the starving and bulimia, when you start to eat normally agiain your body wants to store everything because its unsure when your next meal will be , after time your body will get back to normal though, Have you thought about talking to atherapist to help aid in your recovery? That helps out tons! I would see a dr about he stomach pain because with bulimia and laxative abuse you could have done damage to your body so i would see a dr to make sure thats not the case. ALdo the heartburn could be caused from the bulimia as well, Id go to he drs and get looked at and maybe they could also recomment a therapist in your area to help aidyou in your recovery.
If you ever need someone to talk to feel free to PM me anytime. I will gladly read it and respond and try to help in any way i can.