I agree with the PP. I also had a the same thing, but mine was after a DNC. But just wanted you to know your not alone with that feeling.
The 'black' is actually just dark red - it's probably just an old clot. That happens to me, too.
It depends, for some women these type of symptoms come from time to time, but not for all. If you are experiencing pains in your vagina instead of your lower abdomin and heavy dark blood, and this is something unusual to you or you have never experienced, then you may want to see your gynecologist. It might not be normal but it's nothing to get too concerned about. Hope this helps!