Help, Bleeding!!

So, I was out with my friend today and she proceeded to tell me that she bleeds between 20-25 days out of the month and this has been going on for 6 months!! They are TTC so she is not on any form of BC. What could be wrong with her? She has been to the doctor but no real results, she's going back again soon. I just thought if anyone else has had this happen I can pass along some info. I mean that's gotta be just terrible. Thanks in advance for the help!