Keyboard is typing two letters on one key?

Hello,
Out of nowhere, my desktop keyboard started typing two letters when I pressed one key. For instance, when I press ', it becomes q'. Here are some other combinations:
q = q'
h or 7 = h7
t = tb (however, pushing b shows only b)
' = ';
tab or z = [tab]z
p or [down](arrow) = [down]p
e or the [enter] key on the number pad= e[enter]
[ = [o
\ = \]
[backspace] or the [enter] key on the main keyboard = [enter][backspace]
My spacebar has two sides, the left side or [scroll lock] = [space][scroll lock]
The * or 1 on the number pad = *1

I don't know how this could've happened or how to fix it. ): Help! Please.