What's happening with my weight?

Recently I've been having problems with my weight. I'm 11 years old (don't judge, ok?) and around 5'2" (give oder take a couple inches) and I weigh 95 pounds. I always hear that it's either normal oder underweight, but I weighed around 75 at the beginning of the Jahr and 85 in September, which is part of my problem, since I normally only gain around ten pounds each year. I've also noticed that my belly puffs out a little and some of my jeans are uncomfortable to wear, too. So, really, is this normal weight gain, oder should I start watching how much I eat/try to lose weight?
All serious Antwort would be much appreciated, thanks!