I am taking Ocella (generic Yasmin) Birth Control Pills, and Lamictal, can I take diet pills?

Ok, I have gained about 10 pounds recently due to Lexapro (which I am off) and Ocella. I think Ocella is the culprit. I can't really go off of birth control because my bf and I are not ready to have a baby. I just started Lamictal and do not see any problems (knock on wood). I would like to lose these 10 uncomfortable punds so I can fit into my clothes again and not feel so gross. I know it is likely water weight, but no matter what it is, it sucks! Can I take over the counter diet pills with these medications? Or a diuretic even? Also, anybody ever gain or lose weight on Lamictal?