Hi!
It sounds to me as though you might have what we call a missed abortion. That is the medical term for a miscarriage that isn't complete. In other words, the pregnancy stops developing but the tissue is never expelled. If you were my patient, I would suggest an endometrial biopsy. This is an office procedure which is relatively quick to do, and not terribly painful. It would allow us to find out what the tissue is that they are mentioning on the ultrasound. "echogenic foci in the endometrium"--that basically means sludge within the uterus. Everyone has free fluid in the pelvis, so that is nothing to worry about.
It sounds to me as though your pregnancy test must have been negative in the ER, so I am not too concerned about a tubal pregnancy.
I think that the biopsy is what you need, because it would clean the uterus as well, so that the bleeding would stop too.
Hope this is helpful!
Dr B
Some the impression i left out by accident,however correlation with direct visualization is recommended as clinically indicated