Every month or so I get these large, circular wounds and cuts on my shins. They are always in the same location. I thought that maybe that I was causing them by scratching my shins in my sleep, because the area gets very itchy. But I started bandaging the area once I first feel them, and the wounds still get larger even while covered. They heal after a few weeks, but then come back. This has been happening for years, but has been becoming more frequent lately. What would cause my skin to cut and form scabs on it's own without any kind of injury, and always in the same location?