The North East club have lost three times in February alone without scoring a single goal and have conceded 10 in the process.
Speaking to Sky Sports after the game, Pardew thought his team were second best throughout.
He said: "The opposition completely dominated us almost from start to finish really and I felt that the team didn't look balanced or right.
"I will certainly have to make changes for the Aston Villa game and expect us to do better."
The home side were without the suspended Loic Remy but Pardew insisted that the Frenchman's absence had no bearing on the result.
He added: "Obviously Loic hasn't been available because of suspension but I don't think that had a major impact on tonight.
"We looked a little bit unsure at the back and nervous and for the first time for a long time we didn't look confident so I have got a bit of work to do.
"It's certainly a worry because of the manner of the defeat. We have got to have a lot more fight on the pitch for these fans."