Let me give this a shot. Im young too and maybe can put it into better words for cmac.??
From what I gather from all the reading, the question of the "edge" of the universe is still unclear. This is probably a bad analogy, but take a baloon for example. Starts off small and gets "infinatly" bigger as air is added. It does not necessarily have a center because it is not expanding from one particular point. It is just expanding. And remember that a balloon can be any shape, not just a sphere.
It all made a lot more sense to me after watching the Big Bang Video on the YouTube link. So try that if you have not.
And also, I read this in one of the earlier posts, the universe is expanding in 4D??, so as time goes on, that is what is making the universe bigger (well dark energy is what is making it expand i think, but that is a different topic) So as time passes, the universe gets bigger, just like your ears get bigger as you age. ha.
And I think cmac is still trying to understand the whole light concept. Yes light can only travel at the speed of light. So there are things beyond our visibility, but that doesn't mean they aren't there. And noone is saying that there isn't.
Ok, if any of that is wrong, or if this makes absolutely no sense. Please don't hesistate to correct it. Im just taking a stabe at it based on what I've read here and on links, and some previous knowledge.