Mackail-Smith was flagged offside when he slammed in a rebound from a Shaun Batt shot at Loftus Road and conceded Darren Ferguson's side have not had much to cheer about this term.
He said: "It's very frustrating and it was a great shame as we were pushing hard for all three points and probably deserved to win.
"I felt I was level with Shaun Batt when he shot and there was a defender in front of him so when I gambled on the goalkeeper spilling the ball I felt I was onside.
"I haven't seen the replay on television but several people who have done told me I was at worst level with the defender. That's the way things are going for us at the moment but there is no point in dwelling on it and no point in having a go at the assistant referee.
"We are all human and we all make mistakes, although it would be nice if one of the tight decisions went in our favour. I've now had more goals disallowed than I've scored this season!"