Make sure you have Formidable styling enabled in both the Formidable -> Settings and the individual form settings.
Compare the form preview page with the form in your theme. Any differences are caused by your theme.
Several themes are adding extra space between field labels, the required symbol, and fields. WordPress adds HTML (<p> and <br/>) automatically, and some themes send it through this WP filter multiple times which adds paragraphs and line breaks inside the form. In many of these themes, you can fix this by replacing [formidable id=x] with
[formidable id=x minimize=1]. This will minimize the form HTML so there is nowhere for your theme/other plugins to add the extra <p> and <br/> tags.
Formidable Pro has the most user intuitive interface I have ever seen.
Justin Germino (Dragon Blogger)
Formidable is by far the best contact form I have seen for WordPress. It is easy to create and has had zero issues with form deliveries. What makes Formidable unique is it’s ease of use and reporting capabilities. Takes all of the guesswork out building a form.