Even medication that causes weight gain it's usually not more than 15 lbs at the worst. Antipsychotics in some classes will cause weight gain  but you just have to be more careful. Steroids can cause temporary weight gain but again 10 lbs or so. Birth control has not been proven to affect weight. As a resewrcher in pharmacology this shit drives me up the wall. Like okay maybe your haloperidol made you gain 10 lbs but what about the other 80?