So The First Day Of My Last Period Was On

So the first day of my last period was on February 14, I had unprotected sex that day before AF began. Yesterday (day 17 since my period) I had bright red blood, it wasn't light but it wasn't heavy either. Today it's gone but I'm having mild cramps and I feel very dizzy and tired. I did have unprotected sex the week after my period was done. I'm very worried and I would love to know anyone's opinion. Thank you