let's make sure we are on the same page:
drive down a road (when its safe!) at about 15mph in 1st.
place the car in 3rd or 4th and floor the car.
do the RPMs and the Speed follow each other closely, or do the RPMs raise quickly (slipping) while the car stays relatively the same speed?
If they raise quickly, then your clutch is slipping.
Did you learn to drive on this car? allow others to drive it? purchase this car from someone who may have done so? All of these will significantly decrease the life of a clutch.
Bleeding the clutch (before someone suggests it) will likely not help, as that only ensures full RELEASE. (it could improve a grinding situation when shifting because it wasn't fully open, for example.) Clamping force is not adjustable through this means.