2 weeks of spotting probably should be checked out by your Dr. You may need to go on progesterone to kick start your cycle again. It's not uncommon, it's just out of whack hormones. Your Dr. should also check that the miscarriage was indeed complete. It probably was as you would more then likely be having heavy bleeding if it wasn't. He can clear all of this up with a simple blood test, and then get things back on track. Don't worry, it's not dangerous or anything, you just need a bit of help getting regulated again I think. All the best to you.
And also, the blood is very dark brown or blackish some days which freaks me out.