Ultrasound says my fetus is 6 weeks 2 days but my gestational sac is 7 weeks 2 days. Heartbeat is normal. Is everything ok?

Most likely. The most accurate measurement of the fetus is the crown rump length. The gestational sac is like a fluid filled balloon, not a perfect sphere. So the measurement of the sac can vary quite a bit depending on what part was measured. If there is already a fetal heart beat, that is a great sign. Keep your follow up appointments with your OB doctor.