My girlfriend did a blowjob and kissed me. then i went down to give her an oral during her ovulation. does that disturbs her menstruation?

Disturbance unlikely: Pregnancy unlikely in such a scenario. That said, couples who engage in penis activities, near a vagina, should always be ready for a cute, surprise baby. If a woman has her regular NORMAL menstrual period, then she is not pregnant. If she still thinks she is pregnant, then doing a urine pregnancy test the week after missing her period, or 3 weeks after having sex, should give an accurate result.