Is this tear trough? Eye bag? (Photo)

I'm 24 and have this line under my eye. I have no visible dark circles. The line also disappears when I raise my head a little bit, or when I stretch out the skin around my eyes, it could also disappear in a different light. And it is actually only a half line. What is this? A shallow tear trough/eye bag in formation? What should I do to get rid of it? I had this 2 years ago after a period of time staying up at night. It didn't change better or worse in these 2 years.