Miscarriage information

So I went to the hospital today and they did a scan going on the fact I was 6 weeks pregnant they said they couldn’t see any signs of a pregnancy 🤰 then did a pregnancy test that was positive then took bloods to check my levels and again on Saturday and I won’t know if it’s going down until Tuesday .. however I am concerned because my glow app said I was only 3 weeks pregnant so surly they wouldn’t see anything anyway ?? I just want closer because I don’t want so be upset then it end up being a pregnancy and I don’t know 🤷‍♀️ anyone else had this ??