Exactly one week ago, I began taking a generic version of Alesse birth control. In that week, I have gained close to 5 pounds. Clothes that fit me a week ago are too tight. There has been absolutely no change in my eating habits, so food intake is not the issue. Is it normal to gain this much weight in a short period of time? I am concerned for my health.

The weight you've added is water weight and it will get to a level where it stabilises. If it becomes an issue for you, lower dosages can prevent water retention (but at the cost of being slightly less effective).