What Causes Prolonged Periods?

I have been having problems with my period. I had one at the end of December, then another very heavy one with a lot of clots and pain 2 weeks later, then 3 weeks after that I started again and it has now been 13 days that I have been bleeding with lower abdominal pain and headaches. Even though its the 13th day the blood is bright red, almost orange. I am 34, married, never been pregnant, and have not been on birth control for 14 years. What could be causing this?