I am 36 years old, and have gained 40 pounds in three months. Is this normal, or is it a health problem??

I want to know if gaining 40 pounds in a 3 month period is a normal part of getting older, or do I need to be concerned about a health problem. I had a hysterectomy when I was 28, but my ovaries were left in. Could this be early menopause?? HELP!!!!!! I am miserable>