There really are no "early signs of pregnancy," save a positive pregnancy test--which you can take two weeks after the event in question OR on the first day of a missed period.
You don't say if it has been less than 100 hours since the unprotected sex. If so, you may still obtain Emergency Contraception.
Otherwise, at this point, you can wait for your period to show up, and book an appointment to have a full STD/STI screening (because if you've had a pregnancy risk, you've also had an STD/STI risk). And you can check these articles out, please:
Safe, Sound & Sexy : A Safer Sex How-To
Advice: Anal Sex
"And when the answer that you want/Is in the question that you state/Come what may..." - Coheed and Cambria, "Blood Red Summer"