10 weeks but sonogram says 6 weeks. Very worried !!

This is my first pregnancy so I really don’t know what’s going on but I had an appointment today I’m supposed to be 10 weeks according to the first day of my last period. They tried to hear baby’s heart beat couldn’t find it then they went to give me a sonogram which showed no heart beat and that I was only 6weeks. They immediately assumed miscarriage but another said they maybe have their calculations off and that I could be only 6 weeks and maybe it’s just too early to hear the heart beat so they told me to come back in 10 days. I don’t know how to feel or what to expect I’m still having all the usual pregnancy symptoms so I don’t know what’s wrong. I just want to have my baby 😓