Bleeding during sex before period is due..?

Ok so in the most simplest terms...My period is due any day now, and I had sex the other night. Afterwards I noticed an amount of blood was everywhere, as if I had had sex on the heaviest day of my cycle....nothing hurt so I just cleaned up and put in a tampon. The next day I went to change it (thinking I had just started my period during sex) and there was nothing on the tampon. So I took it out and five days later still no period. I have never bled during sex before and now my period is a few days late. What is going on?? Please help.