Nothing on scan at 6 weeks

So a few weeks ago I took a pregnancy test and it was positive ..I called my OB/GYN and made an appointment. I thought maybe they were just going to do a blood test and maybe a pap smear. they instead wanted to do an ultrasound... So the doctor did a transvaginal ultrasound and we found the gestational sac where it's supposed to be but the doctor told me she couldn't see anything else yet. the machine was trying to focus on something but the doctor didn't have enough time to tell. The doctor also told me that my uterus was tilted and that was making it even harder to see. she also said that from my lmp I should be around 6.5 weeks but considering I could of ovulated late I could just now be hitting the 6 week mark. has anyone else had this happen and then was able to find a baby? I'm so scared and she has me coming back on 10 days to look again...