I think this is just part of your period unless you are passing large
(dollar coin size or more) clots
. Speaking as someone who had a miscarriage
in my 6th week, I passed large clots and suffered extreme abdominal pain the first two weeks of the miscarriage. I bled for two weeks straight and soaked through pads every 1-2 hours. If you are having a miscarriage after 3 weeks it would not be a fetus, it would barely be an embryo with no characteristics (eyes or head) yet.