When does the clutch feel difficult to press or in another explanation, at which point of you pressing down on the clutch does it feel that the clutch is disengaging? Is it more toward the top of pushing down on the clutch, or toward the bottom of the floor board? When was the last time the clutch was replaced and or adjusted? When in gear, is there any play in the shifter from side to side? How is the fluid level on the clutch cylinder (the smaller of the two containers on the drivers side under the hood) All these things will help in answering your question better.