Last day of my period and my husbands condom had precum. not sure if some went inside when i was riding. can i get pregnant? plan b?

It's possible: It is a very low probability, but it is possible. Pre-ejaculation fluid that lubricates the urethra of the male penis also has a small amount of semen in it. Know that semen can sustain itself for up to 24-48 hours in some conditions as well. So in the end, don't be 100% confident that it can not occur, but exercise caution in all sexual activities and continue to be safe by the use of condoms.