your chances are probably low, you were using a condom afterall, and it did not come right off, and you did not finish inside her, i would guess that any pre-cum would be in the condom anyways.
i dont think theres a chance, but if you both are worried, you could wait to see if her period comes, and then take a pregnancy test just to be sure.

Most condoms have spermicidal lubricant. Your partner should be okay.

Condoms should not be slipping off multiple times though. You might want to check the package and make sure these condoms aren't too large. They should be snug fitting and not loose at all. Using a condom that's not the right size is risky and increases the chance of pregnancy.

Good luck.