@Ben_M is spot-on here: if the form is on your website, returning to your website will always pre-populate the form with your data. This knowledgebase article explains.
To make sure this isn't happening for other people, you'll need to visit the website using an Incognito tab in your internet browser.
I'm assuming you don't have customers telling you that they see your email address on the form, it's just your own experience on visiting your site?
Did my post help answer your query? Help the Community by marking it as a solution "The rest of my advice has no basis more reliable than my own meandering experience. I will dispense this experience... now!"
Two things are likely happening here. First, if you want someone to enter their email every time, make sure you don't have the option enabled to "Pre-populate fields with known values". Also, if you want to test and don't want it to be attached to your record due to cookies, then you will need to use incognito or private mode in your browser so that Hubspot does not cookie you.