As Andrew said, your text should be doing just that.
There is one instance that I can think of that will behave in the manner you suggest, and that is if you have the whitespace property set.
See if you don't have the following in your CSS somewhere:
That will cause text to continue on the same line until interrupted by a line break.
OK, my apologies, not sure if edited or added the mark-up afterwards (didn't see it at first).
The overflow-x property is what's causing the scroll bar to appear. Remove that and the div will adjust to as high as it needs to be to contain all your text.