If the compressor is starting to fail, it will become noisy when the A/C is on. It's very difficult to know exactly what is happening without seeing your vehicle, but there is a chance that the system is low on refrigerant. When this happens, the compressor will not turn on, and you will not get any cooling from the A/C. Have a shop check to see if the compressor is turning on, and if it isn't, have them check to see if the system is low on refrigerant. If it is low, they will need to determine where the leak is coming from.