admin error no access to dashboard

I am getting this error which is preventing me from accessing my back end

Notice: is_page was called incorrectly. Conditional query tags do not work before the query is run. Before then, they always return false. Please see Debugging in WordPress for more information. (This message was added in version 3.1.0.) in /home/antony/public_html/wp-includes/functions.php on line 4137

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/antony/public_html/wp-includes/functions.php:4137) in /home/antony/public_html/wp-content/plugins/pro-sites/pro-sites-files/lib/ProSites/Helper/Session.php on line 29

what is causing this and how can it be corrected

I have granted access