Horizontal Invert

I'm having problems to the invert settings. I just quit the game and then when I logged on back, suddenly my horizontal mouse is inverted. I tried searching the solution in YouTube but, they just give me Vertical Invert Settings. I tried looking all the settings but I clearly seen none about horizontal mouse. Also, reinstalling the game didn't help at all. I don't want to reset all off my settings because it will be harsh to set it all up again.

 I'm mainly using a soldier not a vehicle.