6 weeks empty gestational sac

Someone please share their story with me. Went for my 6 week appointment (we did IVF, so this was to confirm the pregnancy was in the uterus and to make sure everything is moving in the correct direction) and it was a difficult scan. I have a tilted uterus, so it was shadowy and hard to see anything. When the doctor found the gestational sac, there was nothing in it. They said to come back in a week. I’m going to go crazy during the wait. Has anyone else had a 6 week scan with nothing and then by 7 weeks they saw baby and heartbeat?? The dates cannot be off because of the IVF. thanks for reading