94 Sentra Revs, has no acceleration

I have a '94 Nissan Sentra which has a clutch cable replaced about 3 yeras ago. Recently I have been noticing the engine reving in all gears. I basically have no acceleration and it is virtually impossible to get the car over 40MPH. I thought I may need to adjust the clutch cable, as the clutch was extrememly hard to press in, but that has not worked. Does anyone have any ideas?

bump

Time to replace the clutch.