In the Pons Dictionary (Latin-German) I found that "pensare" is the intensive form of "pendere", which means "to weigh" or "to weigh heavy", wherefore it is translated in German as "erwägen", which in English is something like "to ponder".
The whole phrase then could be translated as "I was pondering in my memory".
What confuses me is that "pensebam", having the "e" between the "s" and the "b" doesn't seem to come from "pensare" at all, but from something like "pensere". But in no dictionary I have found the entry "pensere".
Is "pensebam" just an irregular way of saying "pensabam"?