Very worried...please give input to help :(

I'm almost 7 weeks... with my first two pregnancies (boy and girl) I had every symptom in the book along with morning, noon, night sicknesses.

This is my 3rd pregnancy and I have no symptoms beside tender breasts. This worried me because of the change from the last two previous pregnancies. So I called my doctor and told them I was concerned

The doctor did my blood levels and progesterone. They were 3600 and prog. was 26. They said this is good but I have to back and make sure they double in 48 hours

2 days later went back and did my blood, got a call progesterone about 28 which is good. But my hcg only went up about 2000. So it didn't double.

They want me in to do a U/S in a week. No cramping or bleeding at all. Should I be worried. Of course I am but I just wanna know what you guys think.