What are the symptoms of a miscarriage?

For the past week, I've had severe cramps 2-3 times per day which resulted in light bleeding and discomfort. My period is not set to arrive until this coming Sunday and I've felt disgusting all week. Earlier today, I was in the kitchen and lost all control as to what I thought was my bladder but turns out it was just water. When I got to the bathroom, there was a clot about the size of a large pea surrounded by what looked like skin cells. I'm unsure as to what is happening with my body and have an appointment tomorrow with my family doctor. I'm just very nervous right now that I miscarried?