If you want to gain a few pound you simply have to eat, especially in the morning, and not miss any meal for that matter. As for getting fat in a month, I won't give you advice for this. It would be like someone wanting to lose 100 lbs in a month, it's just not the right thing to do to your body. You can bag up cereals, or granola, fruit, nuts, seeds or yogurt and eat them during the day, even though your have a hectic schedule. Get up earlier before school starts and eat, Is the best advice I can give you.