98 blazer a/c is having problems HELP!!!!?

Its extremely hot where I live, well the a/c when i first start the truck runs fine, but not the best. after keeping the engine running for about 1 hour worth of driving, the cold air stops, and its kinda like a window unit when you turn off the compressor, it just blows normal air. I popped the hood and touched the compressor in the truck and it was realy hot. well i turned the a/c off and drove about 30mins and when I turned the a/c back on it blew cold air. i stopped and opened the hood and the compreesor was cold again. im confused, can it be a bad compressor? HELP ASAP!!!!!