I only knew the exact date of my last period with my first. At that appointment it was just a pap, and the dos and donts of being pregnant. They did a doppler but that was because it was at 12 wks. I don't believe you will hear a heart beat on that at 8 wks yet.
With the other three, I didn't know the exact date, so had to get an internal ultrasound to give me an EDD. Honestly, with my second, I pretty much knew the date but I wanted to see my little bean so I kind of played dumb, lol!