Challenging if you're not that familiar with word-processing … but it sounds to me as though the first place you need to look is the settings for your e-pub conversion. (is that part of 2008 for Mac, by the way?) What I'd expect is an option to say "start new e-pub chapter every time you hit this style" – so you'll probably need to get your head round styles as well, but that is always recommended.
[btw – note that I used the word chapter and not page. epub files don't usually have pages]