If not, have you been tested for Polycystic Ovarian Syndrome (
PCOS)? That can be a cause of both
infertility and weight gain. However, if you ARE undergoing hormone treatments, like Diane said, it could very well come from that. If you are not on anything, I'd consult a doctor because any unusual weight gain may have a reason behind it.
I was diagnosed with PCOS 2 years ago, and the five years before I was diagnosed I gained 60 lbs (about 27 kgs).