Pereira went into the game having signed a new contract, but the 3-1 defeat leaves Wolves winless five games into the new Premier League season.
The Portuguese manager said: "The first half we are not aggressive under pressure, especially the defenders. They played with a lot of space. We were not doing our pressure in the way we need to do it.
"We are trying to correct the mistakes, but they happen again.
"The second half was different. We didn't conceded anything to them. We were not in the best level defending in the first half.
"We created some chances to score int he second half, but it's not easy because they defended with a low block."
On results dictating his future, Pereira added: "I am not worried about my future. I don't need to answer because I am not worried about my future. I am worried about the results. Of course I am confident I can turn it around."