Oh Amber,
So sorry you're having to go through this {{{hugs}}}
I'm guessing that as you posted this last night, the worst will be over by now.
If not, the best advice I can give in to try & relax and breathe your way through it - big deep breaths.
I'm guessing that the pain is kind of rhythmical, if it's anything like either of the two miscarriages I've had, and is therefore going to be very similar to labour contractions.
It will go on for as long as it takes for your body to expel all that it needs to
Both my miscarriages happened overnight and probably took ~12hrs from the contractions starting up, to the passing and then the contractions easing off.
Thinking of you x x