Sensitivity problems.

So my sensitivity in game is 0. But when i go to look at it and i press the back button to change it, it goes below 0. So what really is my sensitivity? Did it go up to 1 or is it at 0 and there is a mysterious -1 sensitivity? This is really confusing for me and this bug has been going on for years now. You guys really need to look into this. Its like my sensitivity resets every time i go into a new server.