What is the universe expanding into?

In other forums I have been told that the universe is expanding but is not expanding into anything. I would appreciate your views on this subject. My reason for most everything I inquire into is to prove one point. That is to prove that Infinity Exists and therefore there never was a beginning and therefore no creation. There may have been a singularity for the visible matter but I am not convinced that all of the dark matter was part of it. I think the universe is expanding into an Infinity of dark matter which also contains an Infinity of other universes in varying stages of birth, life and death.

I do wonder how you visualize something in your mind that you say was a singularity smaller than a proton that becomes the size of this universe but doesn't actually expand or expand into something. Are you just accepting what someone theorized or can you actually visualize something getting bigger without getting bigger or getting bigger without taking up more space? I believe that when any kind of seed is planted it grows in size by taking in matter from outside itself and that a universe would be no different than anything else.

Can anyone prove that the universe doesn't take in matter from outside? For instance, do neutrinos go to the edge of the universe and just stop or do they continue on into "empty" space and possibly on to penetrate other universes? Could we be exchanging neutrinos and other matter with other universes?
Can anyone prove that the universe is not expanding into something? Personally I think it is irrational to think that something the size of a pea suddenly becoming the size of a basketball does not take up space it did not previously fill.
The problem with believing what the evidence show is that as we learn more we find that the evidence we once accepted becomes erroneous because we find other factors that alter the conclusions we have already made. Like the age of the earth and the universe continues to change.
I'm afraid I have a serious problem with accepting anything, that I can not visualize, just because someone who is an expert and has studied it a great deal tells me that they have the evidence to prove something. Ministers and priests have also studied what they believe and can tell you the same thing.
It would not suprise me that in the distant future someone was to discover that an atom has no empty space whatsoever but is filled with matter, like a liquid, made of particles far smaller than what we are now capable of seeing. In other words find that there is no such thing as nothing anywhere in Infinite space. Well, I guess thats enough rambling on.

That may be true but it sure seems like some of the theories out there are exactly that. "Making shit up". Brane theory sure sounds that way. It seems like their setting around making up things that are so far out that they could never be proved so they will be accepted as a viable theory.