Ok, I was messing around with this guy around 1 a.m. on August 20 but we didn't have sex he was just fingering me and his penis was just rubbing my vagina. I woke up around 9 am on August 20th and got my period. I then had sex with my boyfriend multiple times after my period had ended and found out I was pregnant on September 21. Also my OBGYN told me my pregnancy is 3 days ahead of schedule and moved my due date from May 27 to May 24. Could I possibly be pregnant from the guy that I hooked up with one time on August 20th? Or am I just being paranoid and I have nothing to be worried about? And what does it mean when your due date is moved 3 days ahead?

Sure you could be. It's not as likely but it's possible.