Please see a dentist that is a TMD specialist, to be sure it isn't your JAW not sitting correctly. After that long of bruxism, you may have damage to the TMJs. Even if you do obtain a mouth guard, if it isn't set just for YOU and YOUR TMJs to put your jaw into perfect position, it won't do any real good and may make it worse.
It could be because you are off muscle relaxers, which helped the jaw muscles relax so they didn't pull excessively, and now they can. It could also be that you have worn your teeth down so far that there's no "seat" for your jaw to relax in/on, and thus it's a constant effort.