I don’t know if pregnancy is possible but I’m late

TMI WARNING

I had sex on the second day of my 10 day long period. It was unprotected and I’m pretty sure he came inside me. I am now haven’t one day late and haven’t started when normally I’m a day or two early. I’ve tested and it said negative but it was the really cheap test. Could I be pregnant? Is that even possible with such a long menstrual cycle and it being on the second day? The only time I’ve ever been late is when I was pregnant. Nothing has ever made me late before.