Keyboard glitching, typing more than one letter

Hi. I recently bought a Toshiba Satellite C660D, Windows 7. Lately, my keyboard has been typing more than one letter when I press certain keys. I haven't installed or downloaded anythiing that could a have caused thuis, I did a virus scan and nothing came up (I use ESET security). My arrow keys are having problems too. I use them to scroll the page when I'm not using my mouse, and sometimes the up and across keys won't scroll up and across if I've been using the down key. I'll try to scroll up, but it will just keep going down.

y78 - y (this comes up when I press the 7 and 8 key too)
ui - u and i keys
hk - h and k keys
j, - j and , keys

Y&* - holding in shift and pressing any of those keys

This problem has gotten really annoying, and I'd like to know what the problem is.
Thank you.