I think there are a few questions you need to answer, along with a more detailed outline of your general finances using the standard template.
On top of that, the following would be useful.
What was the understanding of who would pay what and for how long? Was there an agreement verbal or otherwise, or was it just some adhoc arrangement since the breakup?
Is there a reason for her stopping to pay?
I think at the end of the day, you are going to have some comunication with her in order to sort out an situation that you are both liable for, and come to some arrangement for the future.
What is the house worth (take a very pessimistic figure, as the market is very pessimistic now). Are you in a negative equity situation?
If so, can you rent out a room in the house?