Hi, I think these questions can be answered by M-theory, or what has recently grown out of Superstring theory.
Here are some links:
Home Pagehttp://www.damtp.cam.ac.uk/user/gr/public/qg_ss.htmlhttp://arxiv.org/PS_cache/hep-th/pdf/9805/9805177.pdf
I think the gist of the speculative origins of the big bang come from the energy of two colliding "branes." This caused a bubble to form and expand, the energy of the collision is what gave us all the matter and energy in our universe.
I think the notion of there being "nothing" before the BB is becoming outdated. It was really popular conception of the BB since really physicists just said that the theory breaks down at a certain point (at the Planck time and when the universe was at the Plank length.)
What is Planck length? What is Planck time?