'where I got up to' is something like 'the position that I had finished working'. For example, you are marking a test. You stop, because you are tired. You need to find 'where you got up to', so that you can start working again from there. You go through the paper, looking for the place where you stopped. Or maybe you were clever, and put a sticky piece of paper to show 'where you got up to'! 'The weeds have grown so fast, that I can hardly see where I got up to when I was weeding last week'.