Bleeding

This month my husband and I decided we would ttc for baby number 3. I have never tracked my ovulation before our first two kinda where surprises. My last period was the 6th of this month thru the 13th and According to the calendar my full ovulation would have been around the 20th. We had intercourse for 5 days straight to try not to miss it. But on the 23 after intercourse I started bleeding and it didn't end until last night. What would cause this? Any opinions are appreciated.