Klopp's side have now won just once in their past six Bundesliga outings, and Saturday's result means they have lost three consecutive home league games for the first time since March 2000.
Marco Reus' seventh-minute opener looked to have set the hosts on their way to a desperately needed victory, but two individual errors cost Dortmund dear as Hertha turned things around.
At the halfway stage of the season, Dortmund are 12 points adrift of leaders Bayern Munich having played a game more than Pep Guardiola's side.
"We can use the break very well," he said.
"We have things that we need to think about. Something that has started very well, ended very modest. That's how it feels now."
Klopp was typically blunt when assessing his side's defensive shortcomings.
"The second goal was not good, it must be said clearly," he said.
"We have let Hertha Berlin come back completely unnecessarily."
