[Proofrock]

I haven't read the other replies yet, so hopefully I'm not repeating too much of what has already been said. I think your two pair is right at the junction between easy fold and easy push. I lean toward a fold, because I don't see any one-pair hand playing the way Villain does here. An ace either calls down or raises the flop. A worse one-pair doesn't usually bluff like this after you lead both the flop and the turn. Also, Villain puts in a pretty solid raise (raises about 2/3 the pot, and about twice the size of your bet). Given that you've shown strength by betting OOP on two streets, I think a raise from Villain needs to be taken seriously.

The lack of preflop raise from Villain suggests to me he has 55, JQ, 10/10, K10, or maybe AK, in roughly that order (55 and JQ might be switched in order, only because you have a 5 in your hand).

I fold.