I put my penis outside v. no penetration. no cum. just pre cum. both are wet. we do it on 17/8 and my gf got period on 24/8. possible to get pregnant?

Most likely not: The act by itself can put her at risk of being pregnant but since the time of the contact was not in the ovulatory cycle ( safe period ) and she saw her next period couple of days later . So she is not pregnant

Not pregnant: It is nearly impossible to get pregnant without penetration. Furthermore, the fact that your partner had her period means she is not pregnant.