Best Answer - Chosen by the Asker
Outside of adding a comma after 'So far', I think they could both be used.
The only reason that I favor 'been catching up' is that there is not way to confuse it with the notion that somebody is catching you up (bringing you up to date). The first sentence could conceivably be interpreted that way.
However, if you used either one, no one would correct you and in the context, you would be understood.
