If your username is being used for logins, then it has been compromised and it would be a good idea to change it, as this is your first line of defence.
I would always ensure that you use a nickname in the Wordpress user profile, otherwise the username will be listed against any posts that you publish. Also, under Wordfence - Options - Login Security Options make sure that "Prevent discovery of usernames through '?/author=N' scans" is checked. Finally, in some SEO plugins (such as Yoast's Wordpress SEO) there is an option under the sitemaps tab to "Disable author/user sitemap". I had the same problem of a compromised username and the above steps have prevented it from happening again.
Good luck!
Barnez