Yes, it's a silly question, but someone on here might know.
My bf puts his hand on my back and says, "Wait, why is your spine indented?" And, sure enough, there's a big crease down the middle of my back if I'm standing up, and my spine's in a sort of deep groove. He doesn't have it. I haven't felt many backs (who has, really?) but I don't think most people have indented spines. Do I have a posture problem? What is this?