Moniter blinking

Hi, a newbie here and a noncomputer literate person too. I have a emachine ET1331G-07w with a Dell flat screen moniter. The problem I am having is as I sit at the computer the moniter blinks and then changes font size. This seems to happen when someone walks by or while typing or as you bump the desk. It also happens as you sit there and read a page and not move, I checked all connections and all wires are conneted good. The other thing I noticed is while on a message board I type a message and the webpage will have to "recover" itself, not sure if that is related. Last, most of the time I have to click twice on a link. Any help would be great, thanks ahead of time.