Hiring the services of a professional REALTOR® is the first place to begin.
Have your agent do a CMA or comparative market analysis of what the current value is.
This then gives you an idea of what direction to go in. Are you going to have to do A SHORT SALE OR WHEN YOU DO SELL ARE YOU GOING TO HAVE TO BRING MONEY TO THE CLOSING TABLE?
If the agent can’t come up with a true value you may have to invest in having an appraisal done.
The market is what it is and the comparables are all public knowledge and it might not be what you want to hear. But if you are in a financial bind it is time to face the facts.
Get some direction and get your yourself out of the situation.
If you have skipped payments and are facing foreclosure there are options out there as well. The key is communication and documentation. Consulting with a professional REALTOR® is the place to start.