Confused on how many weeks I am

Heather

When I first went to the doctors I thought I was 7-8 weeks but the ultrasound said 5 weeks. Then this past Monday I went and the ultrasound says I’m 10 weeks + 1 day but the blood test paper said I’m 11 weeks + 3 days. The app says that I’m 9 weeks. What do I go by?