1999 GMC Sonoma scraping noise

My truck is mking a scraping noise. It use to do it about once a week and now it does it all the time. It will make the noise most often when I am turning left. The noises sounds like it is comeing from the back right side of my truck. I figured it could be something with the brakes. It sounds pretty bad and it will also make the noise sometimes when I am just driving straight going slow. It does it even when I am not brakeing. Can you give me any help. Thanks