I'm 18 years old and I started my period on February 18th, my periods last 3 days and are always regular. But when I had unprotected sex it was on the last day of my period on February 20th. I also had unprotected sex the next day (21st). My period has been 24 days late (got this app because of this reason) and I've had almost every symptom of pregnancy. Any advice ?!