I Have Lost 90 Pounds With Diet And Exercise. I

I have lost 90 pounds with diet and exercise. I have maintained that weight for about 4 years. I have pcos and am having trouble losing more weight (i have about 50 more to go). I began Belviq about a week ago and have gained nearly 4 pounds!!! This very unusual for me. I am continuing to eat healthy and exercise 4-5 days a week. Discontinue the Belviq? Is weight gain possible? What medication for weight loss do you recommend?