thanks for writing.
with fetal pole
is a positive sign for pregnancy
But as you say your cardiac is faintly visualized that too on doppler and your size estimated was 6 weeks 3 days, this could be worrying.
This is because considering your LMP you are around 9 weeks.
Lag of 3 weeks in growth is quite significant provided you are sure about your LMP.
These lag in growth and cardiac activity not visualized increase chances of miscarriage
But you should definitely go for a repeat scan before any decision.
Wishing you all the best.