I can not log on to my Imac and am having keyboard issues.

I have had my Imac since 2009. Currently I have the El Capitan operating system installed but I still have the original

OS X disc that came with it. I am the only one who uses it so my account is the only one on it. I setup a log on password for security protection. Today when I tried to log on it would not accept my password. I tried entering it multiple times and it would not work. I tried resetting my password via the master password technique but I could not recall what my master password is. I then restarted and went into recovery mode. However, when I tried to type resetpassword in the terminal box, my keyboard would not type the correct letters. I would start typing and rese would appear on the screen but no "t" and word would always come up wiord or some other derivative. I tried typing it multiple times looking at my keyboard to ensure I was hitting the right keys and still nothing worked. I am not sure if this is a keyboard issue or if my Imac is infected. I would greatly appreciate and assistance anyone could give me