[The_Bends]

I fold here.

If the action had gone, lead/call, lead/call, check/push then its an easy call. However with the action going check/call check/call push/? then you can all but eliminate a bluff. He's simply waited for you to be commited to the hand before getting aggressive himself. You can only win if he's playing terribly. Without a read I'm not going to assume that. KJ or a flush I expect.