Yes
Yes
Yes.
Yes.
Yes.
Yes
yes,miscarriage is a great risk of a 3 week pregnant woman.
No they can not.
Yes and even earlier.
If the doctor examined you after the miscarriage you are not pregnant anymore. He would've caught it. It takes several weeks for the hormones to settle so that might be it or you are pregnant again.
Possible if you took no protection and were ovulating.
you usually wont have a miscarriage after your first trimester (third month) after that you would just have a still born baby.