If I'm having trouble loosing weight, is there a hormone responsible for that?

Yes and no. Hormones all play a role in our bodies homeostasis or equilibrium. Weight regulation is a part of that. Infrequently, a "hormone problem" like we see with cortisol excess or thyroid disease can cause trouble with weight loss. By far, though, the biggest reason people have trouble losing weight is not enough exercise or insufficient calorie restriction. I'd focus on those first.
Thyroid? If your thyroid is normal and you have no evidence of adrenal disease, you could have pcos. Check w/your doctor. Diet and exercise may help, no matter what the cause.