You may have an account but not be logged in sometimes. If you do have an account, go to your home node (type your account name-user name- into the search box at the top) and click user settings near the bottom of your page. Just a short way down on the setting page, you'll find a "Theme Configuration" box. If you select one of the non-default themes, it will be clear to you whether you are logged in.
Good Luck