Hi Thomas,
That shouldn’t be happening if your WordPress account has the role of “Administrator”. If you accidentally changed your role to one of the s2Member protected roles (something that WordPress shouldn’t allow you to do in the first place), that might describe what’s happening.
Are you logging in directly to the admin interface or using a login widget on your site? If you’re using a login widget, try logging directly into /wp-login.php. If you’re using URI Restrictions (Dashboard -› s2Member® -› Restriction Options -› URI Access Restrictions), you may have accidentally configured something that incorrectly redirecting you.
You can also try disabling the s2Member plugin manually by using FTP to rename the s2Member folder in /wp-content/plugins/. Renaming the folder to something other than /s2member/ will cause WordPress to disable the plugin.
If that doesn’t work, you’ll need to manually change your user’s role back to Administrator in the database. For that, you’ll want to search Google for instructions and/or post a question in the WordPress.org Support Forums.