Jaquta gave you the answer I would have given...its very unlikely that zolfot is the cause of your weight gain, so look to the birth control pills or anxious emotional eating...if it is the latter, go to www.shrinkyourself.com for more information about what to do about that.
Sometimes when medication(s) are discontinued the unresolved underlying issues can come to the fore again resulting in stress and the use of maladaptive coping strategies (like emotional eating for example).
I don't know much about medications but I know that some can stimulate while others can suppress appetite. Some types of birth control have been said to cause weight gain.
Keeping a food diary may help to identify any areas of your diet that may need addressing.
Poor sleep is also been said to affect weight loss.
There are several ideas. I would think that you've probably made some very subtle changes to your diet or exercise routine that you're unaware of. (Or its the meds which I'm clueless about).
J