I too, had a strange foreboding feeling in 2000 about an impending doom for the world, as I have on many occasions particularly when I was young. However, seeing as nothing major happened within a reasonable timeframe, I didn't connect this to a possible future event. I think that's a gigantic leap to take with no actual reason, and the danger is that then you will spend the next few years with a paranoid mind connecting that feeling with either real events or whatever your imagination cooks up for you. I have since dismissed the feelings I had as a random chemical imbalance in the brain.
I've also had the sideways lurching feeling a few times, and again, I rationalised it away as a strange internal screw-up. I could, at 3am, probably convince myself that during that sensation I was at the centre of a beacon that was pointing Eastwards, but then I could probably also convince myself that an angel was sitting on my chest slapping me in the face and telling me that I must pack my things and make for the North Pole to receive God's Final Message. Point is, come morning I've switched my brain back on and realised that it was probably just a severe brain fart.
So I guess what I'm saying is, I believe these feelings that you've had, but really you're just connecting dots at random and letting your imagination run away with you. I wonder if really you just want your life and experiences to mean something in the wider context. Consider me, who, when something screwed up happens in my head, assumed that something screwed up had happened - inside my head. It was ME who had the strange foreboding feeling or the strange sensation, why should I think it has anything to do with the entire world? More importantly, how do you pick which disaster your premonition or feeling refers to? So your brain is capable of predicting your uncle's stomach cancer and a progression of the end of the world from 2009-13 inclusive, but nothing else - isn't that really quite a strange mix, seeing as your dangerometer didn't react 'up or down' at all at 9/11? How does a sideways feeling of someone pulling at your ankles have a geographical focal point on the other side of the world, let alone three separate ones? Or did you happen to have Google Earth and a compass on you at the time?
It's a strange human condition that has never really touched me, this need to justify what happens to us in some spiritual or supernatural context, that anything unexplained immediately becomes not only mystical, but dangerously important for the whole of the human race. I wonder if its because some people fear not just death, but the insignificance of their death. So they want to go out on a bang and also claim the right as a prophet into the bargain. It cements for them a larger truth and therefore a chance at an afterlife, and an afterlife where they're going to find that they had a divine purpose and importance after all. I applaud your impressionable and creative mind for being able to make such massive leaps in logic and cause-and-effect, and all I can wish for you is that you find a way to distinguish your imagination from reality so that you could write an interesting novel instead of ending up a raving crazy.
Truth is, something might happen at the Olypmics, of course it might. Rationally, a multicultural event in a Western city may of course be a target for terrorism. But that will have nothing to do with your prophecy, and it will not be the end of the world. You're getting strange vibes and your imagination is connecting '2012 oh crap the Mayans were right' and 'Olypmics in a Western country that some factions in the rest of the world hate' with your own heightened sense of doom.
As for the stomach pains, seriously... how was your first thought not, oh crap, my uncle had cancer and I have stomach pains, I should go to a doctor? Or am I just a raging hypochondriac?