Confused and worried

Kristina • Trust me, I'm a lab tech🔬

Based on my LMP I should be at 11 weeks today. I had a BFP on Jan 20th. I had an ultrasound yesterday and I was measuring at 5 weeks. Theres a sac but no baby. I had an HCG done on Feb 7th which was 2047 and one today which was 2657...what is going on? I havent had any cramps or bleeding yet.