Had unprotected sex during ovulation. five days before period i was bleeding red blood with no clots and had cramps and backache. what can this be?

Bleeding P/T menses: The bleeding that you experienced may have been the bleeding associated with implantation. I suggest that you perform a home pregnancy test around the time of expected menses. You may be pregnant!

Possible early: It could be an early pregnancy loss,implantation bleeding or early menses.Try doing a urine pregnancy test.If this bleeding or pain persists then go have a gyn exam to be evaluated for possible infection