Return Key always double spaces

Return Key always double spaces

When I single space a document, the single spacing works fine.  If I complete a sentence mid page, and hit return, it always double spaces.  I want to prepare a document with single spaces so when I export to my blog, there are no spacing problems.  I am unable to place the cursor a single space below the last sentence.  If I use the space bar to go to the end of the line, then it autmatically single spaces to next line below.  It would be simpler to hit return and go to the next line as a single space rather than holding space bar down.  Any thoughts?  Thanks.  Bill Sterling