why are they telling me im 4 1/2 weeks to 5 1/2 weeks when i

i had sex on march 28,29 and april 1 i found out i was pregnant on april 17 and they told me i was 4 in a half to 5 in a half weeks pregnant.. they also said i was pregnant during my period which was on march 16 to the 23... when did i get pregnant???? before or after.... please help me

They caculate your pregnancy from the first day of your last menstral period so when you consider that technically you are already 2 weeks "pregnant" when you become "pregnant" For instance My LMP was Jan 20th I concieved Feb 3rd and on the 4th i was already considered 2 weeks pregnant. By the time you miss your first period you are already 4 weeks pregnant even though you concieved 2 weeks ago. Does that help?