Ok, I was messing around with this guy around 1 a.m. on August 20 but we did have sex he was just fingering me and his penis was just rubbing my vagina. I woke up around 9 am 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 pregnany 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?

Either man could be the father but it's more likely that the boyfriend with whom you had intercourse is the father.

As for changing your due date by three days, he probably calculated wrong the first time from the date you gave him for the start of your last cycle or the date estimated, and was just fixing his error. Medical science cannot tell if a baby is 3 days ahead of schedule as you put it in development - it's not that exacting. That's why babies are almost never born on the "due date" barring a scheduled cesarean or inducement. They can tell roughly how far along you are from ultrasounds, and calculate from your cycle but it's always a rough estimate.

Since you're having unprotected sex with multiple men, you should advise your doctor and be tested for STDs so, if any are present, you can be treated and protect the health of the baby. Just a precaution - not a moral judgment.

First due dates or even conception dates are not exact days. Conception dates are always give or take a week at best, sometimes two weeks.

So if you had sex with two different men within one or two weeks of each other, yes either could be the father.

And yes precum can get you pregnant, so yes it could be the first guy.

Sounds like there is only one way to be sure, get a DNA test done after child is born