I missed my period in the month of December. Then I got it 3 weeks ago and it was light with no cramps (unusual for me). I was also extremely exhausted all the time, like I could sleep all day almost. I thought it was over, then it started again and has been very heavy since, sometimes with huge clots. At times I have moderate cramps, and sometimes just lower back pain. What's happening? What should I do?

What is your age and method of birth control? These are important factors in giving you an accurate "guess." Only your physician can give you an accurate diagnosis.

Go and see your doctor!