Feeling Very Scared

I began to get cramps and brown spotting when I would wipe this past Monday. It instantly flew me into a panic, so I called my RE's nurse. She stated that it's perfectly "normal" to spot during pregnancy. She stated that I have nothing to worry about. However, by Tuesday the cramping continued and the spotting continued. By the time I got up in the middle of the night to go pee (late Tuesday night/early Wednesday morning) I was passing nickle-sized brown blood clots. The cramping this morning (Wednesday) is noticeably stronger, especially in my lower back. And upon going pee this morning when I got up, I continued to pass brown blood clots. There isn't anything noticeable on my panty liner (thank God!) but I am beyond worried. I have also noticed as of this past Monday that my morning sickness has substantially subsided each day. These are not good signs. I am scheduled for an ultrasound this evening, which was already scheduled a week ago. But I can't help but feel that perhaps my nurse maybe should've taken me a bit more seriously. All she told me to do was to do as little physical activity as possible. I am especially concerned, since last week my RE took me off of my twice daily progesterone injections to simply a morning progesterone vaginal cream. It seemed like a pretty drastic change in the amount of progesterone to me. And progesterone is the very hormone that helps a miscarriage from happening!
I am left feeling helpless and angry from feeling that there's nothing I can do, but lie here and wait for my appointment to come this evening. I am praying that when he does my ultrasound this evening, he doesn't tell me that one or both of the babies have stopped growing and have died; hence the brown blood. A huge part of me will have died with them if that is the case.