As the Word application has changed over the years, which version are you using? Your version might have different procedures than mine.
Are you generating a new document or converting a document that was previously generated that you are loading from the hard disk? Are you setting the "Save As type" as HTML in the "Save As..." pop-up?
Is Word's style setting for the text set to "Normal"? The style setting may be in a drop down that also offers three "Heading" styles.
Have you checked the Paragraph "before" and "after" spacing? The Paragraph formatting pop-up could be on Word's "format" menu.
Does the text have hard carriage returns? These should appear in your Word window as paragraph marks when you have Show/Hide spaces/paragraph marks enabled.
Open the saved HTML file with Notepad. Locate places where your paragraphs started and ended. Are there paragraph tags ("</p>" at the end of a paragraph and <p> at the beginning of the next paragraph) or break tags ("<br>" or "<br/>") in those areas of the file?