So I have always been regular,I'm 20 btw. I missed a period for the first time in my life. All pregnancy tests said neg. so a week later I started my period right on time but it was so light and after a week I kept bleeding and it was super heavy and that lasted another week so I had a two week period. It's been 4 days since I Stoped bleeding and i started bleeding agin! What could be wrong?