Is it possible for me to get "swimsuit ready" in 7 weeks?

Well I gained 28 pounds and I have only 7 weeks before the day I go to a waterpark and wear a swimsuit. I'm 5' 2 and I weigh 138. I want to lose atleast 20 pounds in 7 weeks by eating less junkfood, mostly veggies and fruits, and water and milk only. I was going to exercise 5 days a week too for an hour atleast each of those days. Is it an okay idea?