Bears coach John Fox is taking heat in Chicago today, both for the dumbest challenge of this NFL season, and generally for his 12-29 record as the team’s head coach. But Fox says he’s not feeling that heat on his seat. Fox was asked after Sunday’s loss to the Packers if he’s worried about his job, and he said he’s not. ‘‘I’ve been doing this too long to ever worry about my job security, and I won’t start any minute going forward,’’ he said.