You should have at least a small amount of freeplay in the pedal before it starts to release the clutch. If not the floorboard is partially releaseing the clutch. If that is the problem get under the truck with 2 3/4 open end wrenches & adjust the nuts on the clutch link so you have about 1/2 in. free play at the pedal. If that's not the not the problem you need a new clutch. If it is getting oil on it you will need to take care of that also.
