If your website’s admin account (or the one you use to post) uses the same email as your WordPress.com account, it will use the profile picture you add at https://wordpress.com/me
If not, go to Gravatar.com and sign in with your WordPress.com account. Add a new email and verify it, then assign the image you want to that email address.
It looks like you might have a second WordPress.com account under the email used on your site, so try logging in with that email and setting up the Gravatar profile image under that account. The website you add to your Gravatar profile does not affect how your profile image is used, and it’s all tied to the matching emails instead.