We got to hear the heartbeat on a Doppler last week at 10 weeks and 3 days.
However, it wasn't easy to find, and I felt BRUISED for 3 days after! (Seriously, all the pressing really hurt. But it was worth it.
) We only caught 2 quick "glimpses" because the baby was "swimming around in there." Not enough to record the bpm, but enough to hear a strong and healthy hb!
FWIW, my midwife said 8 weeks was too early, but she was confident she could find it at 10 weeks, even though this is my first babe and I'm not exactly super skinny.
But you might have a chance at 8 weeks since this is your 3rd!