I just reread your message, and I think the issue is that the piece you looked up for guitar is in a different key than in your piano piece, which would explain why it sounded weird when you tried to play along. C natural isn't in the key of E, so it lent some dissonance.
My bad. Transpose it, if you don't know how, I'm sure a handy person on GT will step up, 'cause I gotta split. Good luck.