Mac Problem - When moving the mouse moves the entire enlarged screen

I’ve owned my iMac for just a few months now. I love it, but the most frustrating hiccups I’ve had is when I’ve had my toddler, Rocco, on my lap and he’s gone crazy on the keyboard. He’s already renamed my hard drive, but the worst thing that happened was when the whole screen became larger and would move around with the mouse. It really freaked me out. It makes the computer only just usable. Just usable enough to try to find the fix. Read more . . .