Hello, and I hope I can help you today.
Even though your boyfriend's penis was inside you for only a short time, sperm can be present in
pre-ejaculate (or pre-cum) and if you truly do not want to become pregnant it is really important to avoid any contact of the penis with your vagina during sexual play.
The most fertile time of a woman cycle is in the middle, typically 14 days before your menstrual period would be due. So the time from when your period finishes until you start to feel PMS symptoms is your fertile time.
So in this case, since your boyfriend did not ejaculate, it still would be quite rare for you to have conceived. The most common sign of
pregnancy is a late or delayed menstrual period. So in your case, you just need to wait for your period to arrive, and if it is late, you can do an over-the-counter urine pregnancy test which is greater than 99% accurate. Pregnancy test do not become positive however until at least 2 to 3 weeks after conception.
So in summary, your chances of having gotten pregnant in your particular situation is very very low. For the future, please make sure that the penis is completely covered with a condom if it has any contact with the opening of your vagina. As long as the area is moist, sperm can swim all the way up your vagina from the opening and result in pregnancy. However, the amount of sperm in pre-cum is extremely low so again I doubt that you need to be concerned about this one sexual encounter.
I hope that I was able to adequately answer your question today, and that this information was helpful.
Best wishes, Dr. Brown