My girlfriend got drunk at a party on the evening of 28th february/ (early morning of 1st March) and is pretty certain she had unprotected sex with someone else but cant remember for sure (but the guy has told her), she then came on her period on March 3rd, but she said she was feeling quite tired for the next 2 weeks. My girlfriend and I then had unprotected sex on march 16th. Her menstrual cycle is 28days. She did a pregnancy test the day after we had sex, and it came out negative, she then did a clearblue digital one on March 27th and it was negative, she also did another clearblue digital one on March 30th and that was negative too, this would be around the time she was due on her next period, she did another 2 normal line test ones on March 31st and they came out faintly positive.
Can someone please help me to find out if I am the father, obviously I don't want to do a DNA test 9 months down the line. So is it possible for her to have gotten pregnant a few days before her period, how accurate would the ovulation tests be? Help me!!