In the middle I guess
No clue
None
1. "Middle" what? When did you get the mouse?
2. It shouldn't be that hard figuring out what the mouse is. Microsoft? Logitech? It should be under the mouse if you can't find it anywhere else.
It's most likely your mouse. I had this same problem when my old Logitech mouse gave up on me, probably when I spam-clicked it.