I suppose it is better to be too cautious then not enough. I would be pretty frustrated already too. I hate going to the doctors office I have to be on my death bed to go. That is likely why I have gone with a midwife for both my pregnancies. I really dislike dealing with the doctors. (& I work in hospital)
I am glad to hear that all your tests are coming out good. After 22 weeks the ultra sounds are not too accurate because the baby is getting big and harder to measure. So I wouldn't get too worried about babies size. My DH has 3 brothers and all four were over 10lbs. They are all 6'2 and taller! So I don't know I am not a doctor but some babies are just genetically big, or if mom is a big women naturally chances are the baby will be bigger.
Good luck to you and the baby, I hope you don't have to push out a 10lber but if you do...........all the best! Ouch!