So after my period ended last month I made a mistake and had sex with a coworker. It was unprotected but the next morning I bought and took the plan b one step. A few day later I had spotting heavy enough to use a tampon and it lasted for like 2 or 3 days. I was supposed to start my period last week. And I took two pregnancy tests and they came out negative. What is wrong with me and why haven't I gotten my period?