Hey My Name Is Brittanie I Am 3t Pregnant And

hey my name is brittanie I am 3t pregnant and I had sex with a guy on the 12th of feb and I got my period on the 3rd of feb and it ended on the 9th of feb and before that I was having sex with my partner a lot and also I have been have irregular periods and I have done the calucations on when I was ovulating and it says I wasn't ovulating on the 12th of feb so how does the irregular period and ovulation work if you having irregular periods??? I just wanna know if its my partners baby or the other guys kid???