Getting hidden pages with I use "Section Break"

You do not need a page break if you insert a Next Page section break. If you insert an Odd Page break (or if Word converts your Next Page break to an Odd Page break), then you will get a totally blank even page at the end of the previous section if that section ends on an odd page. You will not see this page in your document unless you are viewing facing pages in Print Preview.

If you have enabled "Different odd and even" or "Mirror margins" (either of which will suggest to Word that you plan to duplex the document), and if you are restarting numbering at 1 in each section, Word will insist on starting the section on an odd page and will therefore change your Next Page break to Odd Page (though it may still display as Next Page).

Sometimes it is possible to change the section start type on the Layout tab of Page Setup, but not in cases such as this where Word insists on making page 1 an odd page.

Also, just in case there is any misunderstanding, you do not need any section breaks within your chapters in order to omit the header on the first page of the chapter; simply enable "Different first page" and leave the First Page Header blank. You will need section breaks between chapters in order to have a First Page Header for each chapter.

For more on headers and footers, see http://sbarnhill.mvps.org/WordFAQs/HeaderFooter.htm. For more on blank pages, see http://sbarnhill.mvps.org/WordFAQs/BlankPage.htm.

You sometimes need to change the section break settings after inserting them.  If you click on the View ribbon and click the Draft button in the Document Views group you can check that you haven't got extra Next Page section breaks inserted accidentally.  If you are printing double-sided then you may need to use Odd Page or Even Page section breaks to force the next page to start on the correct side.  If a section break is giving a blank page, click just after the section break and then click the launcher button in the bottom right-hand corner of the Page Setup group on the Page Layout ribbon.  Click on the Layout section of this window and use the drop-down box beside Section start: to set where this section should start.

Extra lines at the bottom of the previous page may also force your section break one page further on than you expect.