I Have These Three Perfectly Straight Scratch Marks In The

I have these three perfectly straight scratch marks in the same place on off for months. I changed bed because I thought It might be something in mattress or pillow. I changed pillows! It's around my shoulder blade area on right back. It is not my clothing and I have no animals. It's very strange and I am getting concerned. I only really realize they are there when they starts to itch and i scratch not realizing yet another time I have these marks which by the time I scratch them they have a little tiny scab and I guess it itched because it's healing. What the heck is this? I am not a mental person just saying this is truly happening and it is starting to freak me out because it's been going on several months