Weird period

My period for this month was supposed to start September 6th, and it did. I think. Last night, September 5th, I was feeling frisky and fingered myself. When I was done, my hand was all bloody so I put on a pad and went to bed assuming I started my period. I went to change it this morning and there was nothing on my pad, and I put my finger in my vagina and it wasn't bloody. I haven't bled at all anymore today but I've had a little cramping. I've been on birth control for about three weeks, is that why it's weird? I had sex seven days ago, we used a condom and he didn't come in me so I don't think I'm pregnant.