If I had sex on April 12 and again on April 19, which day did I get pregnant

You probably won't be able to tell the exact date.

If I had sex on april 12 and again on april 19, which day did i get pregnant

When was your last period? The dates are so close, as emily said, you may not be able to tell, but knowing when your last period was may give you somewhat of an idea. Although dna testing is going to be needed with dates that close if you are trying to determine the baby's father.