Under-pressure United boss Van Gaal is facing even greater scrutiny after his side suffered a shock 2-1 loss to Norwich at Old Trafford.
It was United's sixth game without a win in all competitions, their third successive defeat and a result that left them fifth in the Barclays Premier League.
Asked if he feared for his position, the Dutchman said: "Yes of course I am worried about that because I know that belief in a manager is very important, and when you lose the games you play then the belief in a manager shall decrease
That is happening now
I cannot close my eyes to that."
But asked if he still believed in himself, Van Gaal added: "Yes, I think so
I don't think a change of management shall bring direct success - but that is what I believe
Maybe that is not so interesting."
Van Gaal does accept that things are not going well, admitting United's current run is one of the low points in his extensive managerial career.
The former Barcelona, Bayern Munich, Ajax and Holland manager said: "I am always evaluating myself because I think that is an aspect of the philosophy I have
But the philosophy is also making an evolution - I am not the same coach I was 25 years ago.
"So, you are always evaluating and of course that philosophy is very important for me
Because of that I am - or maybe I have to say now, was - a very successful manager."
United started brightly against the Canaries but did not test opposing goalkeeper Declan Rudd and were caught out by breakaway goals from Cameron Jerome and Alex Tettey either side of half-time.
Anthony Martial pulled one back as United rallied in the closing stages but it was not enough.
Van Gaal said: "What you have seen today is what a lack of confidence can do
It was not good enough
It is also confirmation we are in a very bad period and we have to come out of that bad period.
"You have to win against Norwich City, you have to win every home match
We did that this season until now
The problem is how we can manage to come out of this bad period.
"That can be done when you are sticking together, not only the players, manager and staff, but also the fans, because that is very important."
Norwich's victory - their first at Old Trafford since 1989 - lifted them out of the relegation zone and manager Alex Neil felt it was thoroughly deserved.
He said: "One thing about Louis van Gaal's teams is they start quick
They press you high up the park and are really in your face.
"You need to make sure after 30 minutes you are in the game and then the game will become bigger and it gives you the opportunity to pick up wee pockets and try to hurt them on the counter
That is what ended up happening.
"I thought the players' work ethic was incredible
Many a team have come away from home against bigger sides and sat behind the ball and ended up being done by four or five.
"But we limited them to very little at times and posed a threat on the break
We showed good quality in certain areas on the pitch.
"I wanted it so badly for them and I thought we deserved it
I'm really pleased."
Source : PA
Source: PA