Roy Keane picked out Stern John's disallowed goal as the key moment as Town were held to another goalless draw by Peterborough.
The Crystal Palace loanee headed in from Jon Walters' cross just before the break but referee Andy Hall awarded a foul against the striker.
"Saying it was harsh would be an understatement and it was the turning point in the game," the Town boss told the Club website.
"We didn't play particularly well but we had chance after chance and it was the same old story.
"We played too many long balls in the second-half. I don't know why because we don't encourage the players to do that but maybe it was a sign of us getting edgy.
"We over complicated it at times as well, when you are looking at players to have a shot when they are in a good position.
"It's very frustrating. The only positive is that we kept another clean sheet. Our defensive record is outstanding at the moment and if we had turned any ratio of chances into goals we would be so much better off in the table."