Chances of getting pregnant from a small amount of precum without a condom

My boyfriend and I have had sex before, but always with a condom. Today we didnt have any condoms but were really in the mood, so he put in it for only like 3 seconds then pulled out. He had already precummed a few minutes before that, but it was wiped off by his clothes. And that precum isn't have any sperm in it since he hadn't ejaculated recently. A few minutes after the pulled out I gave him a hand job and he finished, but not inside me of course. 2 hours later we got home again and started snuggling for an hour and he precummed in his clothing again, but he hadn't used the bathroom in between since he finished. So three hours after he finished he put it in me again for only a few seconds, and his penis was dry when he put it in. But since he hadn't used the bathroom, his pre had sperm in it. I don't think he precummed inside me since he had already a few minutes and more time before that, but it's possible he did. What are the chances of me getting pregnant from him being inside of me for only a few seconds? Were scared and aren't ready to be making decisions about children and such, so please help me. Thanks