I agree with opal. Remember that pulling out isn't a reliable form of birth control and neither is, "Well, he wasn't in there for very long." Pregnancy can happen just from a man putting his penis inside a vagina for a second or two and even if neither person has an orgasm.
Also, even if you take the pill exactly as intended (every single day, and at the same time every day), it is very effective, but not 100% effective. So make sure you use a backup method of birth control for at least seven days, if not longer. You have a few options other than condoms too.
We can't tell you exactly how likely it is that you will get pregnant from this, but we can tell you that it isn't impossible.