if you click single space and continue to type until it starts a new line, it should be single space, i know its stupid and frustrating but its designed for you to continue to type and it will single space, it sucks. that might be the problem
Check under Alignment & Spacing > Paragraph Spacing - set this value to zero. You can change the normal template also instead of changing this each time.
I had to open the Normal Style, and click the move lines closer together. than i saved the style, and all was well. That is also how you can change the normal font.