Am I gaining the weight I've lost?

Okay after a month of intense exercise and eating healthy, I lost 4 pounds. Well it was during the holidays and I have plenty of time to exercise. But now, I'm back to school. I feel like I'm gaining weight but I'm not sure? I came back after a game of team handball and I have just put on 1 kg ?! I didn't stop exercising but I just exercise less, maybe 3 times a week now. I didn't stop eating healthy either. God, I'm scared. What should I do? I don't have much time these days, my exams are just around the corner. If only I had time to exercise everyday! :(