Help me please

my last cycle was 8 days long and I’m not sure why. It’s a new month and my period was supposed to start 2 days ago and it hasn’t. I had sex exactly two days ago and even though I’ve had sex before I believed my hymen popped but I thought it was my period coming on until I stop bleeding shortly after. I’ve been cramping a week so three days prior to me having sex but my period still hasn’t came on and I’m still cramping off and on