Hcg levels


So on the 26th of November I had my levels checked at the hospital they were 1540 they did an ultrasound and said they couldn’t see anything yet because I was too early but wanted me to come back wed 28th to have them redrawn .. I did and they were 3756 .. fast forward to my appointment last tue 11th they took my blood and today 17th I’m finding out the results the nurse said they’re 65,000 ..but she said they aren’t rising how they should so I’m doing an ultrasound tomorrow .how are they not ? Lol according to my lmp and this app I’m 8 weeks today.