99 grand am scraping sound

Hi all. I have a 99 Grand Am SE with 3400 V6. Recently, the a/c (still working), if not on makes a high pitched ringing sound. If i turn it on, the sound stops, but the engine sounds like it is really working overtime to keep it going. When I turn it off, the engine chills out and the ringing starts shortly afterward. But most recently, I turned the car on and as I was idling out of my parking space I heard this strange scraping, squeeling sound -- very similar to the noise of when nails on a chalkboard, or the sound from the squeel bars when brakes go. After it drives for about 10-15 seconds, the sound goes away. I have no idea what it is and am nervous to keep driving it without damaging anything major. Can anyone help? p.s I already checked all fluid levels and they are good, but the car was making a few noises before this major one started, if i was turning sharply from a standstill.