Who is your publisher?
There should be a clause in your contract regarding release options. Or you may simply have to wait until your contract expires in a few years. What does the contract say regarding different formats? Did they say they WOULD release in paper and now they aren't? Or did they say they just wanted the rights?
Have they released other authors in paperback? Was that precedent already set when you signed the contract?
They might release you from your contract, but it can be tricky business. They're really under no obligation to release you once you've signed. If they refuse, you may have to go to court, at which point you have to decide if your potential lost income outweighs your legal costs.
As for paying you back the money you made on your book -- did you receive an advance? Have you earned it out? Have you made any royalties above and beyond that advance? You can request an audit of their books if they haven't already provided you with a statement of your earnings.
But those royalties are the only money you make on the book. The other percentage of the profit goes to the publisher, which is what you agreed to in your contract.
Your best bet would be to hire an attorney who knows literary contract law and pay for a few hours of his time to get their opinion. You need firm legal counsel on this, not just some Y/A answers.
And next time you sign a contract, have an attorney go over it with you and explain everything. The cost of his time will save you both money and stress down the road.