Please help! :(

I’m 5 weeks and had a scan done yesterday. The only thing that could be seen was a sac. My levels have been rising nicely and I’m in the 10,000 which is why I’m so confused as to why they couldn’t see anything more as as a nurse, I was under the impression it all went based off your hcg levels. My understanding is we should have seen baby at this point :(! I’m so beyond worried because I’m losing symptoms even though I’m not bleeding. Can someone please provide me some sort of reassurance or even just tell me past experiences? Should I be concerned? Or am I over worrying? I have had 2 past miscarriages so which is why I’m so worried. I haven’t had any bleeding