Hey deljar...

Very sorry that you are having to experience this...
I too had a "no heartbeat" scan and decided to m/c naturally. It was painful. It lasted about 4-5 days, the last 2 in hospital.
I am assuming that they did an ultrasound on you before you were discharged - this will determine whether or not all of the POC was/has been expelled. If they did not do one, request one.
If they didn't do one and you also did not have a D&C, the your uterus will most likely still be trying to expel the POC - this should slow and stop on its own within an week or so (so I was told). If it gets more intense and/or you start bleeding more heavily again, you should go to Casualty straight away. Unresolved POC can lead to serious infections as the blood will become septic. (sorry to be graphic but it is very serious)

Having said all of this, a good warm wheat pack and a warm shower can help ease the pain of the cramps, as can a small increase in your intake of salt (so im told believe it or not!! lol)
If you are at all worried though, return straight back to casualty and ask them to check you out with an ultrasound.

I wish you all the best...It will get better too Good Luck