Ok, so i'm cruising along in 2nd gear, then as I shift to 3rd the rpm's decrease. Then all of a sudden, I shift to 4th gear and the RPM jumps to around 4-5k. This isn't normal because it has never happened like this. Can someone explain why this is happening?

 

Time for a new clutch.

 

yup... drive in 4th gear going about 20mph, floor it. if the rpms jump and you dont speed up, the clutch is going out