I think I figured out why there was duplication of leads going into salesforce from my forms page.
At first I thought it was that users were refreshing the page but on further testing, it duplicated without refreshing.
I had two different salesforce wordpress to lead forms on that page.
When I moved the second form to its own page, I did not experience the duplicate entries into salesforce.
I hope this is the answer to your question too carlosdemon999