See a psychiatrist as soon as possible. You can probably find some medications that will not make you gain weight as long as you're watching what you're eating. Some meds that have helped me without causing weight gain were Lamictal, Latuda, Abilify, and Trileptal. Risperdal in lower doses doesn't hinder my weight-loss efforts, either, but that can be a weight-gainer for some people. I've lost 70 lbs while on meds, so weight-loss and weight maintenance can be done while on meds.

HUGS!! You deserve to feel stable and sane. See a doctor ASAP.