So much weight gain in 2 months is really alarming. Topamac should not cause weight gain and in fact patients taking topamac are known to lose weight. Get your self evaluated by a physician for this sudden wt gain. You may need to get thyroid function tests
. After physician's evaluation a gynecological check up may also be required. Sometimes hormonal
disturbances can lead to wt gain. This doesn't seem to be medication related. Best way is to reduce food intake and increase exercise.