believe it or not, the same thing happened to me! and i didnt do anything about it and now i'm in grad school and only now working to get it all off.. and i have succeded =)
What I have done is start by exercising at least 4 times a week... I usually run, but I also have a kickboxing workout I do and some other things... get into the habit of burning those extra calories =)
Speaking of calories, the other part of my diet has been to cut back on what I eat and space out my meals through the day. I eat 5-6 times a day, about every 3 hours. I have a good breakfast, a piece of fruit mid-morning, lunch, another snack in the afternoon and i try to have a light dinner.. althoug hthat doesn't always work out as planned =)
Good luck! and i hope you find this website helpful