Ultrasound

So I got off nexplanon 8 weeks ago and had no period. I got blood taken 2 weeks ago and my hcg levels were negative. But Saturday I started getting positive pregnancy tests (9 in all). I am not sure when I ovulated. But today I went to the doctors because I was going to start Provera to start my period but of course I didn't have to because my doctor confirmed that I was pregnant also. He did an ultrasound just to try and get a date because I didn't have a period. There was not even a sac on the ultrasound and he said that would be Normal because I wouldn't be able to even see a sack until 5 weeks. I have to go back in 2 weeks for another ultrasound and I also got blood taken today again.

Now is this normal? My ClearBlue says I am 4-5 weeks, so I am guessing I am around the 4 week mark..

I never had an ultrasound until 6 weeks with my other children and at that time I was able to see it.

I just don't want to worry if I don't have to..