 [ Symptoms ] crazy weight gain on birth control  i am under eating i have an eating disorder but getting help and i exercise vigorously for 6 days a week but i am retaining crazy amounts of founding and gaining weight like crazy what is going on i am a teen runner out on the pill to gain a period back [ Disease ] hi doing some research for you found this here on webmd while weight gain is an uncommon and temporary side effect to the pill if you happen to be one of those few women who put on pounds talk to your doctor your doctor may suggest a different type of birth control pill why because all pills are not the same so get back to your doctor asap hope this helps you good luck