question about the universe...

I was hoping someone could help me with the following question. I am trying
to understand something of the size of the universe, and I came accross a
quote that said "the universe is expanding in all directions, and that the
'Cosmic Microwave Background' (the remaining heat from the Big Bang, is
found at a distance of 15 billion light years from us in all directions."

Tow questions result from this:
- does this not suggest the universe is ball-shaped, and
- that the earth is pretty much at the centre of the universe, near where
the Big Bang occurred?

Any input you can give me (in laymen's terms, please) would be welcome!

Rogier