Clutch problems

Okay, so the past few days every time I go to press on the gas it will rev really high like it wasn't getting any power to the wheels. Then once it finally got up to speed the revs would go back to normal until I needed to change speed again. A then tonight I was going up hill it revved to like 6,000 rpm's when I left off the gas some it jerked real hard, but then it was like it was fixed. It didn't rev high anymore and drove like normal until I had to come to a stop. Then it was like stuck in gear an there was hardly any pressure coming from the clutch pedal, I had to force it out of sixth gear and back into first to take off again. Which it was hard to do but it would do it. Also it is hard to switch gears period now. No pressure hardly on the pedal but it revs like normal now and does not go really high like it was does. Anyone have any idea what this could be? I want to figure out what is wrong before I go replacing stuff that don't need to be replaced.