Period day 15!

I've currently been on my period for 15 days that has also been accompanied by cramps. My husband and I are TTC so naturally this has me very worried. A few months back I had 5 periods over 6 weeks. I went to my OB/GYN and he told me just to wait it out. I have another appointment in two weeks and I don't want my doctor to tell me the same thing. I know my body and I can tellthat  something isn't quite right. Has anybody ever experienced this or something similar? Or can anyone help shed some light on what might be going on?