I went from a size 12 to a size 16. complained to all my doctors and didn't get much attention other to excerise. As it turned out I had a huge blood clot. I've lost 25 pounds since the blood clot is disolving. So don't always assume that all weight gain is caused by meds. I'm still not back to a size 12 but I'm getting closer and the clot isn't gone yet. So keep in mind that fast weight gain can be to other factors. If you are concerned check with you doctor.
Gayle