I just got a EH english muff'n and i've noticed a hum that happens when i turn the pedal on. It gets worse when i put the gain and volume up. This hum instatly goes away when i touch the metal part of the pedal or a metal part of my guitar.

I'm pretty sure my guitar is properly grounded because i havn't had this problem before so how can i fix my pedal if it is the pedal (i can take a picture of the inside if i need to).