A family of Microsoft word processing software products for creating web, email, and print documents.
When you press Enter to create a new paragraph, the paragraph spacing kicks in. If you want no additional spacing between double-spaced paragraphs, set the Spacing Before and Spacing After to zero.
The screen shot below shows the Spacing Before / After settings for the paragraph containing the insertion point. You can of course modify the paragraph style you are using so that you have the desired settings there. Or you can change the document defaults.