The latest theory I read about is that at the start, probably caused by two branes colliding (a topic for another time), there was a rapid expansion (some jokingly labeled it the big bang and that name seemed to have stuck) and then it slowed to a almost none at all. From that point it slowly start expanding to the point where it sped up almost exponentially. I saw a picture in Astronomy Magazine that showed a good representation of it so I got into my AutoCAD program and reproduced it:
As you can see, at first there was rapid expansion that slowed to a steady rate but then seemed to expand wildly. Our universe is so large now that light from one side will probably never reach the other. There is no possible way to see the entire universe. I would like to hear your ideas of the universe, how it started, and where it is going. Now, I hope all is well in your universe.