How much creatine should I be taking?

I take about 5g every other day, on the days I do an upper body workout. When I do legs and cardio on the off days I don't take any. I take some whey protein after each workout. I was just wondering if this is even doing anything for me...it seems to at least be giving me some energy when I workout. I feel like this is a way to keep me from getting completely used to taking it and it will help so that when I stop taking it I wont "deflate" as much. Does this sound reasonable?