Most doctors will wait till like 8/9 weeks because you'll be able to see something then ...Congrats on your faint positive I got a faint positive 3 days after my missed cycle and they didn't do a ultrasound/blood work at 9weeks .
I got blood work done when I was three weeks pregnant. And probably not on the ultrasound. Ask you will see if the sac. Baby is far too small to see.
I got a blood test at a little past 5 weeks but didn'tget my first ultrasound until a little past 8 weeks, and that was onky because I was so sick they wanted to check for multiples.