Period 22 days late

Hello ladies my last menstrual period was August 27 and lasted unusually for 10 days (I normally bleed for 5 days). I am recently married so have been having unprotected sex with my partner and he ejaculated inside of me on the 15 of September. My next expected period was to be around September 22 but it did not arrive. So far Ive done 3 HPT & a blood draw which have all been negative. My period tracker currently says Im 22 days late and I only have headaches, cramps and constipation which feels similar to when I was previously pregnant. I was just wondering if its possible for me to be pregnant even with negative readings. Has this happened to anyone and what was your outcome?