**Neither a teacher nor a native speaker.**
Have you already visited this site?
Englische Zeiten (‹bersicht Zeitformen Englisch)
I often go to that site when I want to check some past tenses.
What exactly can't you remember?
Their use (when to use)?
P.S. I believe it's: "I have rummaged around for a while now.", or even: "I have been rummaging around for a while now.", but maybe I'm wrong...
Student or Learner