"Sono stato a pensare a quello che mi hai detto."

Translation: I have been thinking about what you said to me.

[CTrinity]

Why say 'sono stato a pensare' instead of 'ho pensato'??

[f.formica]

"Ho pensato" presents the thought as concluded, while "sono stato a pensare" refers to a prolonged thinking. You could get the same effect with the imperfect "stavo pensando", although that's perhaps closer to "I was thinking".

[CTrinity]

Thanks! That makes sense, although one of the given translations is 'I thought about ...' which would more closely mesh with the ho pensato than the sono stato translation, I think.