Don't know what to believe

Yancy
So this is my first pregnancy & I thought I was about 10 weeks along then I went and got an ultrasound and the lady said I was 21.1 weeks. So I got a blood test and it said I was 2-3 months?? I'm so very confused and haven't seen my obgyn yet bc I was waiting on my Medicaid to come in. I was also on the shot for 2 1/2 years so I don't know when my period should have came. I need help I'm stressing out.