I'm a little new to this, but this might help: convert your .docx file to an earlier Word format, the .doc format. Then save that one as an html document, and it'll be more ready to upload to Kindle for conversion.
Thanks for trying to help me but it didn't work. I got all these funky letters in various parts of the document. when you say earlier word format which version. Should I upload it as a zip file? Maybe I'm doing something wrong saving it as a html file?
Just a quick note to say that you can use calibre (http://calibre.kovidgoyal.net/) on the Mac to create a Mobipocket file to upload to the DTP. That makes it hard to edit the book or make changes, but you could also convert it to an ePub file and make changes to that before converting it to a Mobi.