Jake's in a terrible place this time around. Not only does he have to deal with the fact that he's known forever, that his brother (who's basically his idol) is infested, but now circumstances are contributing to him having to worry about his father becoming infested
Tom can't leave the area for long trips since he can't be outside the range of the Yeerk Pool, not without starving and freeing a very unwilling host who wouldn't just march back to get a new Yeerk
We've seen Jake have to deal with stress before, numerous times, but there's more at stake for him in this encounter than ever before and he seems to be breaking down for real for the first time