Simon Church grabbed a last minute equaliser for the visitors after Paul Hartley had given City a 1-0 lead with a 12th minute penalty.
"Reading deserved at least a draw," Johnson said after Saturday's 1-1 draw..
"We were very poor after taking the lead and have a lot of hard work to do.
"It was deja vu for us as far as conceding a late goal is concerned. Our supporters are getting fed up with it, but we keep telling the players the same things and at the moment it isn't working.
"We gave the ball away too much and allowed Reading far too great a share of the play.
"We didn't create enough chances after starting reasonably well and getting the break with the early penalty.
"I thought we should have had two more spot-kicks, but if they had been given and we had scored it would have been rough justice on Reading."