In some one of those many sections (almost certainly one that's in the
middle of a page), the numbering is restarting. There are two ways to
approach this (once you determine where the problem is):

1. Insert a temporary page break in the middle of the problem section in
order to get access to its header/footer. Then use the Format Page Number
button on the Heading and Footer toolbar to open the Page Number Format
dialog dialog and change the setting to "Continue from previous page."

2. With the insertion point in the affected section, use Insert | Page
Numbers. Click Format..., make the same change, click OK to close the Page
Number Format dialog, and then very carefully use Close rather than OK to
close the Page Numbers dialog so you don't get an extra PAGE field.