First timer here. First thought I was at 8 weeks, based on the last period math. Then went to doc on Monday for my first ultrasound and the machine said u was 6 weeks, but the doctor said something about me being 4 weeks. My due date us may 9...which I put into the app and it confirmed I'm 6 weeks. the fetus was measured at. .4 cm. Iooked it up online and it's a little small for 6 weeks. I am so confused and Concerned. Help!