It does sound like the compressor is locked up or one lead (wire) to the compressor is broken or burned in two or the run capacitor is bad. A service tech. could determine if the capacitor is ok and/or check the compressor by installing a hard start kit. If that works ok. If not then you need to replace the compressor. Either way I'd advise calling a certified Technician. This isn't someting you can do yourself.