My last menstrual period was March 3 through the 9. I had unprotected sex throughout the month of March but am worried about the night of the 16. I started my next period April 1 through the 5 and have had intercourse throughout this month as well. I got a positive home pregnancy test on the 26 so I am wanting to know if I could've gotten pregnant around the 16 of March and had my period and still been pregnant or if I actually became pregnant sometime in April?

There's no way to tell you when you got pregnant. It's simply not possible to do online. Even a doctor can only give you a best guess, it can be off 2 weeks either way even with an ultrasound.

Is this a question of paternity? Is that why the date of conception is important? If so, only a DNA test will answer that question.

Good luck and congrats.