I just published a guide I wrote and the formatting in the preview looked okay, but I searched for it, sampled it on kindle and the formatting is horrendous. Pages are pushed up and start where they shouldn't, spacing is all over the place. It's only been a few hours since I published it and although it appears online, it said it can take a few days to finish? Should things change after that?
If it's live, then anyone who downloads to their Kindles will get what you saw. You might want to unpublish (look under the three dots ... at the right of your Bookshelf) until you get it sorted out. You will then be able to upload a new interior over the old and hit Publish again.
The formatting will reflect what you uploaded. It won't look exactly the same as your word-processed document because a Kindle has reflowable text. If you hit Return at the end of every line as you type, for example, the returns will be in different places on the Kindle. Page breaks will be in different places, because a Kindle is a small screen.
You should hit Return only at the ends of paragraphs, never use the tab key for indents (use "first line special" instead), and use page-breaks only at the ends of chapters. If you did any of these, I'm afraid you'll have to fix things to make your book look OK.
On the main Community Forum page, look to the right for a message about KDP Jumpstart. it has good info on formatting your book.
Then you uploaded something horrendous. Un-publish it and fix it. How you do that depends on what you uploaded and how you previewed it, which you haven't told us. If you're using Word, read the third post in my blog.
(Don't trust KDP to publish a print edition. Don't trust CreateSpace to publish an ebook. Each does one thing well and the other thing poorly.)
The conversion process doesn't add formatting errors, but it does reveal the errors you make. Your allusion to "pages" is confusing because e-books have no pages, only a simulation of them. Also, if you're referring to the Look Inside, be aware that the Look Inside reveals formatting errors commonly suppressed during conversion, so your book may indeed look good in the preview, but horrendous on the sales page. If you created your book with Word, as so many do, but did not format using Styles, then that is likely the source of your problem.