Mine was 165 the other day at 10 weeks, perfectly normal. The tech said it changes all the time too so not to be too concerned with it. I'm sure they'd tell you if they had a concern. Congratulations - hearing the heartbeat is the best! Ours was 135 last time (also normal) at 6.5 weeks and I was so relieved and happy to hear that loud 165 BPM!
I also thought mine was too fast lol & omg thankfully!!!(:
Mine was at that rate at my 8wk appt. I found a chart that says,170bpm is normal until a little after 10weeks. So you're normal and baby is on target. :-)
When I first heard that rate I thought my baby's heart was too fast. Lol