Van Gaal declared Manchester United went on a winning run because of his controversial back three but fans, who objected to the Dutchman's 3-5-2 system, chanted "four-four-two" during their win at QPR last week, when both goals came when the former Premier League champions had gone to a four-man defence.
United have scored more goals and created more chances when they have played with a back four, a midfield diamond and two strikers.
But Van Gaal, in particularly colourful language, believes they allowed their opponents too many opportunities and said those games were too nerve-wracking for his liking.
"I know that with 4-4-2 the stats are giving the positive results [that] we have won more with 4-4-2 in a diamond, but when you analyse the game then we have twitched our ass on the bench," he stated in a news conference.
"I said to my players I was squeezing my ass but it was the wrong expression: I have twitched my a-- on the bench because we were out of balance.
"And all the matches when we play 4-4-2 like against West Ham United, it was always twitching your a-- and I don't like it."
United won eight games and drew three in an 11-match run after their November defeat to Manchester City, although Van Gaal, exaggerating their success, claimed their record was better.
He added: "Maybe then you see after I switch the system we have won nine or 10 in a row. Then we lose one match and then the discussion about the system is coming so it is ridiculous."
Van Gaal said he will continue to ignore the opinions of the press and the United-supporting public.
"I have to take into account 600 million opinions?" he asked, referencing reports that United have 659 million fans in the world.
"I have to communicate with my players and observe my players and analyse my players and my team and my opponent and the quality of my opponent and then I have to make a decision with my staff.
"But I cannot hear or listen to what the media are writing or what other people are saying or writing. No, because they are never at the training ground and not attending the meetings."
Van Gaal also defended his decision to select the most expensive player in the history of British football, 59.7 million-pound signing Angel Di Maria, as a striker, even though he was generally used as a winger or a midfielder before arriving at Old Trafford.
He added: "He played in the 4-4-2 in the left midfield position. In the 3-5-2 he does not play so much because he has been injured.
"Then he came back and I tried him as a striker because we need also pace in our striker's position. We have to stretch the pitch. Then you make the pitch bigger and your midfielders can play in a bigger space and play a better positional game than ever.
"So I tried that because I have to do that because I don't have the preparation at the beginning of the season.
"Nevertheless in the last 15 games we only lost one [to Southampton] and that was undeserved. We were the better team."
