United were beaten 1-0 by Southampton at Old Trafford in the Premier League last weekend and subsequent media reports suggested that the Dutchman, booed by the home crowd, had offered to resign.
Appearing at a news conference at United's Carrington training ground ahead of an FA Cup fourth round tie at second tier Derby County on Friday, Van Gaal came out fighting against his critics.
"It is the third time already that I have been sacked and I am still sitting here for you," he said. "I am obliged to do that [attend news conferences].
"I am very concerned people are believing what you are writing and that you don't have to verify what you are writing."
Van Gaal said he always had faith but had also predicted negative headlines.
"When you lose it is worse. That I have predicted already before the game against Southampton. Now I cannot lose any more because I am then condemned for the fourth time that I have been sacked.
"Maybe then you have written the truth, because sometimes it happens."
The manager thanked United's executive vice-chairman Ed Woodward for his 'fantastic' support but suggested that also put pressure on him to justify it.
"When the board has such confidence in you, then the pressure is much higher than when they say 'it's your last game' or something like that," he declared.
"Then the confidence is not so high and you can fight against it. And when you can fight, you have a bigger motivation than when they support you. I am always fighting."
United are fifth in the league, 10 points behind leaders Leicester City, have won only three of their last 13 league and cup matches and are struggling desperately to produce the attacking football fans have traditionally demanded.
