I don’t understand?

I took 6 pregnancy tests at home. All were positive. Due to my endometriosis, I’ve had miscarriages in the past. (I am TTC) I called my doctor to schedule an appointment. This was 4 weeks ago I scheduled. I went and when I did a urine test it was negative. They set me up for an ultrasound. She told me there was no baby? I had bled for three days, (I called the on call nurse and she told me that if I wasn’t heavy bleeding or cramping I should be fine.) it was just enough to wear a pad but not bad. I didn’t cramp. It wasn’t like any of my miscarriages. They are sending me for blood work. But she said that I had to of miscarry. Has this happened? Do you think I miscarried? Confused.