Ladies only please?

I am 31. My husband and I have been married for 4 years now. (He had a vasectomy 4 years ago so I don't think that I'm pregnant) but anyway: for the past three and a half days, I have been cramping very badly but nothing happens no pink or brown, just nothing. I had a headache last night that was down right aweful but it's gone now. Lately my cylce has been every 21 days and very light and last for 3 days AT THE MOST. Could I be going through early menopause? I am very much healthy according to my gyno. What could be the deal?