How to get out of a lease if the roomate won't sign anything?

My ex boyfriend and I have a apartment together we have 9months left on the lease, all he has to do is sign a form removing me from lease or sign a notice to vacate and they will let us both out of the lease and I can have a new apartment by myself. However, He is refusing to sign anything! The apartment mgr said if he doesn't then I have to still pay for the rest of the 9 months. So basically I am being forced to either live with him for 9months or pay for him to have a full 9months free. He doesn't care about his credit so he has stated he won't pay a dime to me or the apartment. Meaning I will be stuck with the 9 months of rent. What can I do? I just want out and he is forcing me to stay or pay. Please help