From what you say it sounds like something is definitely broken - without removal of the gearbox it will be difficult to acurately guess what it is.
There is a possibility that it could be the operating fork (the bit that bears on the release bearing) - that *should* give you an extremely light clutch pedal - and a lever that you can move by hand at the bell housing (where the cable attaches).
If it is still too tight to move by hand, it is more likely to be a failure in the cover plate (if the pedal is lighter than it used to be).
If the pedal feels as it always did, then the springs in the plate(s) are possibly okay, and it is a failure of the bearing.
In any event, by the time you have stripped it all down to find the problem, it is probably false economy NOT to replace the 3 parts of the clutch as a whole unit.
If at all possible, I would suggest not running the engine until it is done, as any moving parts will probably be out of alignment and can cause wear to the solid castings.