What Causes Prolonged Periods For 2 Months?

Hi, I am 44yrs old. I have always had my period every 28 days. Now I have had it for almost 2 months. My doctor put me on estrogen for 1 week. It stopped for 4 days, but the day after I took my last pill my period came back. I called my doctor and she is now having me get a D&C. What do you think is going on? Had blood test done and everything is fine!