About a week ago, I developed this cluster of red bumps on my lower back. It's very very itchy and I have no idea how I got it. When I scratch it, even lightly, it will sting really bad. When I brush my hand over it though, it just feels like a cluster of bumps and it doesn't hurt. It's hard to control the urge to scratch it and when I do, the stinging is really bad. I live in a neighborhood with lots of trees and grass and I'm wondering if this is Chigger bites, but I'm not sure. Any ideas on what it might be and how to get rid of it?