Have you actually had a positive home pregnancy test or on in the doctors surgery or blood test yet? The way you've written your post makes it look like the doctor is basing your pregnancy on being 3 weeks late alone. I've seen heaps of ladies in here that have been really late but were not pregnant. Did the doctor do an internal exam? Sorry for all the questions but I don't want you getting your hopes up if the doctor has jumped to the wrong conclusion. If you haven't had a positive HPT or a BT yet I'd suggest you get one ASAP so you know for sure. No point putting yourself through a scan if there's nothing there to look at.

It is possible to have very few symptoms early on. I had none with my first one, I just "felt" pregnant. Second one I had a few symptoms by 4 weeks, third one I had heaps by 4 weeks. Everyone is different and every pregnancy is different.

If I've misunderstood your post and you have had a positive test - good luck with everything.