Problem with the size of desktop changing

[king1]

Zooming in by the sounds of it

hold CTRL with the + or - on the keyboard...

But also holding CTRL and scrolling the wheel on a mouse is a zoom function...

Some touchpads also have a scroll track along the bottom and side that I presume might also work with the CTRL key

so check the CTRL button isn't stuck or pressed by a lazy hand, if you know what I mean...