Is it possible to get pregnant if the condom slipped?

ABSOLUTELY. Condoms are only 85-90% effective. The condom may fall off during withdrawal of the penis and sperm can find their way back up into the vagina, through the cervix, up the uterus, and into the fallopian tube where an anxious egg await. It only takes one sperm to penetrate the egg and a male ejaculate may contains as many as 150, 000, 000 of them.
Yes. Condom use is an effective way to prevent pregnancy, but proper use and a good fit are essential. As a result, condom use alone is not the most effective form of birth control.