Open the file in Word. Turn on the format symbols. You may be able to see why the periods went onto the next line. It could be you hit the space bar by accident. I had done that several times before I finished the book.
It is probably something easily correct.
If you are using Word 2007 or 2010, save as Word 97-2003.
I have the same problem. It's not just the period, but any punctuation. Even the apostrophes. When "you're" is in a position to wrap, Nook does this:
After coming in here and finding out that you
're not available ...
I've gone back and checked for spaces before the punctuation, but have found none. Something's up with the newer software updates to Nook. I have 50 titles up including short stories, and it does it for all of them on my color Nook and Simple Touch. However, it doesn't do it on my Android Nook App. The odd thing is this: Those titles first put up over a year ago, never did that. As Nook updated it's sopftware, it started happening (and to the ones already in place) and I can't find a way to beat it, nor do I hear from anyone else having problems trying to upload their Word 97-2003 files.