Dortmund's 2-1 loss to FC Koln in the Bundesliga yesterday was their three successive defeat and extended their winless run to five games.
Klopp told FIFA.com: "We played a type of football which makes absolutely no sense. We had a high number of failed passes and committed simple mistakes which really hurt us.
"We have to correct these errors. Not tomorrow, or the day after, but now. To concede two goals in each game is rubbish. We have to sort this out and no one will help us do that."
Dortmund will be looking to find their form again when they play Galatasaray in the Champions League on Wednesday.