Please.. I need help.

On Saturday, my boyfriend and I, had intercourse. We did have protection(condoms) but however, after transitioning into a new position the condom slipped off. We didn't know for one minute while is penis was inside of me. It was night time and we had no light on to see if it was still on. I felt his penis and felt no condom on him. I got up really quick and told him where did it go until we saw it right by him. We got a new condom and finished what we were doing. He DIDN'T ejaculate inside of me. But, could precum get me pregnant? He did urinate an hour before intercourse. He was in the restroom for about 20-40 seconds. Could I be pregnant from precum? and is there a way to prevent pregnancy.