How To Confirm Pregnancy After A Prolonged Delay Of Periods?

Good day doctor, ay we please have your advise, My girlfriend and i had unprotected sex last august 27, september 2 & 3. Do note that what i meant by the unprotected sex was, at first grinding naked with her afterward i did put it inside her for like less than 30 seconds then back to grinding. Afterwards i masterbated and ejaculated outside of her long before i felt like that it ll come out. Also i did pee before and after each sex. Her last period started august 19 - 23. Shes having an irregular period. Average of 30-35 days. Base on the foregoings, is there a high chance thats shes pregnant? Right now she seems okay and somewhat no changes at all. Or syntoms of pregnancy. But ofcourse since we are expecting her period this week by sept 21. It makes her stressed which may eventually cause delay. Please advise if shes pregnant. Best regards