About a month ago I had unprotected sex... I know, I'm dumb, but it happened. He came inside- even though I told him not to... I took a Plan B pill two days after the occurrence. About 4 days after taking plan B, I got a really light period. It only lasted for two days but it was so light there was almost no point in wearing a pad or tampon. 1 week after that I took a pregnancy test just to be safe and it showed negative. My period is currently 1 week late. I took a second pregnancy test and it also showed up negative.  I'm currently having symptoms such as acne and light cramps but my period just isn't here. Should I be worried? Has anyone had a similar experience?