You can get back on track now - you don't have to wait for summer. Do your best to eat nutritious foods and get exercise when you can. This is a lifestyle change, not just a "diet." When you diet, that gives the meaning of temporary and you will end up doing that off and on throughout your life. I'm sure you don't want to do that, so take this time to change your habits. You don't have to be perfect and you don't have to do it all at once. Make some small goals and work on those at first and the rest will fall into place.
Take some time to check out the Resource Center too. There is plenty of helpful info in there.
Here are a few articles that you should take a look at:
i am having a hard time keeping on track with my diet i am slacking really bad. i am so busy i am having a hard time fitting exercise in my schedule i want a nicer body for the summer but i will be able to get back on track during the summer because i wont be in school i need help. charlotte