It's full of Dirt, Lint and Hair.
Suck it out with a vacuum cleaner, spin the wheel as you do it.
I think he(she) meant the touchpad, side/top finger touch does not sound like a "mouse".
Go to your vendor's web site, and download the drivers and software for the touchpad. There is usually 2, one is the driver to make it work, the other a utility software to configure it in Windows.
This is not touching on the fact that it could have just gone bad.