I had unprotected sex during ovulation, 9 days later i bleed for a brief time (2 hrs) 10 days before my scheduled period. the bleeding since comes & goes. i get negative pregnancy test.what's going on?

Hard to say: There's always the implantation all bleed, it could be anovulation, or cervictis, bottom line is are you pregnant. It could be a very early threatened pregnancy loss. Try and relax if you wanted to you could check Progesterone a d HCG levels, but most commonly low Progesterone comes from a pregnancy destined to fail. If you are healthy just wait . Time will declare your course the rest is guess.