HTC Droid Eris : Letters Go Moves - When Im Typing Sometimes

Im new to HTC. I am actually very satesfide with my eris. Except for just recently. My eris for some reason changes pages and slides on its own when im not touching it. and when i hold the phone its gets worse. How can i fix this? Another thing. When im typing sometimes the thing that says were the letters go moves and my words look all messed up. Example: im typing the word mississippi.. and halfway Threw the word it moves making it look like this --> sippimissis.. i dont eventouch that part of the screen.. one last thing.. when im ussing the internet on. my eris sometimes the phone clicks things randomly. It presses random buttons by its self :/ seems to me theres a senor/ touch problem. How can i fix all this?