Continuous Bleeding

So, this is something that's been happening to me for over a year. My husband and I have just started to try for a baby, since July. I've been logging, spoken to my doctor, had exams, everything seems normal. Every other month I literally bleed for 20 days, some days more than others. I've asked questions but everything appears normal. Also, I bleed after sex, there is no pain, everything is as normal as it always has been but I just won't stop bleeding.

Does anyone have any experience dealing with this? Any tips or suggestions?