Have you discussed this with your doctor.....perhaps dividing the dosage or adjusting the times may help. How much do you take and when????
And how long have you been on it??? Perhaps by exercising a bit and watching what you eat you can curb the weight gain a bit. I know when my daughter gained weight she was able to lose most of it by doing this.
I am glad to hear that it is helping. Let us know how it goes.