My phone is tapping on stuff by itself. Why?

My phone usually reacts to my touch, but the past week it has been acting up. Such that it starts tapping on stuff that is displayed on the current screen. It acts as if I am touching the screen when Im not. At the same time my home key, back arrow, search key (Magnifying Glass), and menu key sometimes work and sometimes they dont. When they are not working its at the same time that my screen is tapping on stuff by itsef. Also it just doesnt tap, it taps and holds sometimes. I replaced my LCD and digitizer several months ago, around Sept 13. It has worked like a dream since then until about a week ago. I also did a factory reset to my phone, about three days ago, 2-21-13, thinking that might fix my phone, but it did not work. Should I replace my digitizer again? Any help or suggestions would be gladly appreciated thanks in advanced.