BC question

Jamie
Ok ladies, I am 25 and have only been sexually active for 2yrs. I was once on the pill ....I'm terrible about taking meds & terrified of wt. gain (I've been in recovery from an eating disorder, but I still have a lot of issues surrounding it). I definitely need to be on BC though because I'm in a steady relationship & we are sexually active. I'd prefer an IUD. Anyone have tips/experience with anything you like & has a low chance of increased weight?