It is normal to bleed heavily and pass clots when miscarrying. The heavy bleeding, clots and cramps typically last anywhere from 1-3 days but can vary. You will likely bleed for longer than that tho, just not as heavily. I'm sorry you are having to experience this :(
As GA says, it's pretty normal. However, if you bleed a whole lot, or get dizzy and faint, or get feverish, go to the ER or at least the doctor. I was told to go in if I filled a maxipad in less than an hour, but in my case, I would "flood;" when lying down it was pretty normal, but when I would get up to go to the bathroom, a whole cereal-bowl full of blood would rush out. So I did go to the doctor, and finished the miscarriage in the hospital.
Good advice, I didn't think to throw that in!