Please help!

Hi, my period is 2 days late. My cycle is on average 27 days, my last was 26 but the 2 before was 27, and on average for 2020 is 27 days. I last had sex on the 4th October , but I took a clear blue digital pregnancy test this afternoon and it said not pregnant. I do have cramps but they are a lot milder and more spaced out than when I’m about to get my period. I feel really tired and my like bit where your pubic hair is feels really firm whereas usually it’s soft. Is this a serious condition? I’m really worried my period has never been longer than 28 days (I’m on day 30 now) and I don’t know what to do.