How do you think the universe began ?

While I agree with the Big Bang Theory, I don't understand why scientists don't theorize what the universe was before it began..Most say something about the first collision of particles which set off a reaction, but I often wonder if it's like some other religions say - that the Universe remakes itself in a continual cycle. This means that there must have been a Universe before our Universe, that was destroyed so that our Universe could come into being.