Maybe try completely cutting out the diet sodas, I know that may be hard for some (I love soda, regular not diet, yuck) but they're not healthy for you either even if they are diet. Crystal Light is a good option. I would start doing maybe a half a mile to a mile walk everyday or every other day. I'm not trying to say you don't exercise enough or something, I just understand that it is noticeably more difficult to lose weight on certain medications.