A little help....

Don’t laugh please..... okay so, my last period started on June 1st, it was suppose to come again July 1st but I’m late. My husband and I had unprotected sex June 16th and he did not pull out and he did it again that following weekend twice... why is it that when I put these dates in a pregnancy calculator, it says that I’m already 4 weeks and 3 days when I had unprotected sex only 2 weeks ago at most? Im aware that it goes off of the first day of your last period however I’m still confused... can someone better explain this to me?