If the compressor were bad, then it will lock up thus eliminating your belt from the engine bay.
Are you sure that the clutch is kicking in? Do you hear the clutch click?
If there were a blockage, and enough pressure builds up in the system then there is a relief valve in the compressor that will blow off until the pressure goes below the limit.
Check and double check that you have the correct amount of freon in your system. If you have too much, it won't cool.