Hi, i am 8wks pregnant by lmp but first ultrasound showed 6wks n fetus measured 6.4mm(crl) but no heart beat. any chance for viable pregnancy? help me

Certainly: It is not uncommon for there to be a discrepancy between ultrasound and LMP for dating.It would be reassuring to see a heart beat but it may just be too early. If you are not bleeding, there is a good chance that a repeat ultrasound in a week will show a normal heartbeat. Good luck. It sounds like you will be a great mom since you care so much.