Re: how do you know when you are miscarrying
If you aren't having excessive bleeding, don't have a fever, and don't have any other physical or emotional symptoms you can't cope with, there isn't any need to go to the ER. If it is a miscarriage, they can run some tests and do an exam, and verify that it's a miscarriage. They can't stop it, and there's nothing they can really do to help. You can still take a home pregnancy test. Even if you are miscarrying or have miscarried you will often get a positive result. The pregnancy hormone leaves your body very gradually. With some very early miscarriages you will get a negative pretty quickly, because the hormone levels didn't rise quickly enough, but generally, if the pregnancy did start to develop, you'll get a positive if indeed you are or were pregnant.
I've had three miscarriages. The first was early, I was scared, I went to the ER. I got a bunch of tests and interventions, and still had a miscarriage. The second one I stayed home and let it happen on its own. It was like a period, but somewhat more painful, more clots, and more light bleeding for longer than with a period. With the third, it was a later miscarriage, at 9 weeks. I stayed home until I started having troubling symptoms, like fever and increasing pain, and then I was able to get a same day appt with my OB, who helped fix the problem, which was that the miscarriage was incomplete.
The first one, in the ER, was by far the most traumatic and disturbing, even more than the later one with real medical complications. Unless there are symptoms of a medical emergency, an ER is a terrible place to have a miscarriage. Miscarriages are often about just waiting for it to finish so you can move on. ER's are about urgency and fixing the problem. The two things don't go together very well.
Just my opinion, based on my experiences.