i don't know when i got pregnant

Im pregnant but dont know when I got pregnant. My last normal period was feb 11 and lasted the normal amount of days. I then had unprotected sex on march 4th I believe he used the pull out method. On march 10th my period came a day sooner and lasted about 3 days which was not normal to me but I didnt pay it no mind. Then I had sex on march 17th and again on march 26th. I have not gotten a period since. I took a at home pregnancy test which came out positive very fast. On which day could I have gotten pregnant?