Messed up Clutch?

Had a problem like a month ago where it felt like my clutch was slipping...I replaced the bearing and clutch while I was in there..the clutch didnt look too bad but since I had it ripped apart I replaced it anyways..problem went away...now it is back...what happens is whenever a certain amount of tourque (dunno thr rpm no tach) is applied it just runs the engine up and the car kind of skips like power is going to the wheels then it isn't...since i know now that it isn't the clutch..anyone know what it could be??