mouse is possessed!

Hi...I've had my iMac for two years now, and haven't had any problems. My two year old got a hold of the mouse, and now it's going crazy! It's switching back and forth from the regular screen to the F10 screen where it shows any pages that I have open. It will also alternately go into that light blue highlight mode. I'm likening it to trying to catch a fish with my hands. Any suggestions?