Lately I have had consistent 25 day cycles. We had unprotected intercourse on CDs 5,6,13,&14. Today I am on cycle day 16 (which is going on to cd 17) and spotted very lightly for about 2 hours. Only noticed when wiping. Is there a possibility of pregnancy? Could this be implantation bleeding? Or is something wrong? I am also experiencing mild dull cramping very low in my abdomen.