yes,miscarriage is a great risk of a 3 week pregnant woman.
Yes.
Yes
Yes.
Yes.
Yes
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.
4 weeks pregnant is when your period is due, this may be a period or if it is really heavy and you have had a positive test I am afraid you are probably having a miscarriage.
You know that you've had a miscarriage when you're screaming in pain and a dead bloody fetus comes out of your vagina. And you can be three months pregnant and not realize it without a test depending on your body weight