Conceiving before period?

So typically my period starts the 3rd week of the month and lasts about 5 days. Heavy bleeding and hellish cramps. But in April, my period never came. My SO and I just sort of assumed i was pregnant again. So we had sex unprotected and he came in me. I took a few tests and they came back negative and then my period came, finally, the 1st of may and ended today. The 2nd. No notable cramps other then some tinges in my ovaries but nothing like a period. Could I have gotten pregnant right before my "period"? Or was I pregnant the whole time and just dont have enough HcG? I figured the egg had died already so I couldn't. What do you think? Is it possible?