Well, implantation bleeding
usually occurs around the time your period would occur, so I don't know if it would be implantation bleeding. How long ago did you last have unprotected sex? You can test with a first response early response test two weeks
after sex, and if it's negative, test again when your period is due, and you should get a positive if you're pregnant. It might just be your period coming on early, or it could be an infection (the brown) Good luck! I hope you get your BFP!