I had a US at 5 weeks because of AF like cramps and all they could see was a sac.
at 8 wk US heartbeat 167 bpm

Dr says cramping is normal at around the time AF should have come

Try not to worry which is hard I worried all the time but I'm getting better at relaxing now at 14 weeks.

Congrats by the way , crossing everything for you

Luv Jelly