OK, now I understand what is happening. You need to make the toolbars with formatting options go away in your FrameMaker and NEVER touch them again. Formatting should NOT be done with those functions. In fact, formatting should not be done at all except by wrapping a piece of text in a <b> element, which is available from the Element Catalog.
If you are working in FrameMaker 11, the safest way to edit your documents in a more or less WYSIWIG fashion is to use the Author View. If you are working in an earlier version of FrameMaker, simply hide the formatting toolbar so that you cannot make this mistake anymore.
Good luck
Jang