So what's up?

simple question, 'whats up?', ive been answering all such questions as 'how are you' 'hows it going' 'whats up' etc as 'i dont know' for the past week or so, when i said it to jared we got into this big conversation of how i should know whats up, because before i know it, itll be down, and he spent about 10 minutes talking about how its too much of a downer not knowing whats up, then after the converstion ended he asked me again what was up, and i said things, he said i was doing better
after school i ran into jared and ben on the way to picking up my grades (which by the way, im passing all my classes, two a's one p, and four c's) anyways, ben asked how i was, i said i didnt know and jared said that wasnt good because before i know it everything will be down, and i dont want things to be down, then we got on how 'whats up' is commonly used instead of 'hey', as in people say it to you then walk off without listening to what answer you possibly have, and in the words of ben "they might as well saying 'fuck you' or 'go jump off a cliff', although i think id be more happy if someone said that than walking off while im trying to talk" or something to that same effect, i happen to not have a tape recorder in my head, sadly