Me and my boyfriend had unprotected sex 16 days ago. It was only for maybe two minutes and he never came inside of me. I am also on birth control but left it in my car a couple of times so I don’t know how effective it still is. About two days ago I started having what looked like brown discharge (implantation bleeding maybe). I took a test on Sunday, two tests yesterday and one test this morning and they were all negative. How accurate will the negative tests be if it was 14-16 days after sex where he never came inside of me and my birth control is probably still effective?