There are theories, such as String Theory. There is a theory that White Holes exist - the opposite of Black Holes, and mathematically possible. Instead of sucking in matter like Black Holes, White Holes shoot out matter. So our particular universe could have simply exploded out of the ass end of one of those.
The brilliant Lawrence Krauss has a new book out on this, "A Universe From Nothing",
Amazon product ASIN 1451624468
That's the beauty and fun of science: You always get to be curious, challenge yourself, ask questions, think, experiment, and admit that you don't have all the answers. Awesome!
.