Warning: Cannot modify header information

Im getting this message on all of my pages: “Warning: Cannot modify header information – headers already sent by (output started at /home/x2bingoclub1988/public_html/myurl.com/wp-includes/comment.php:1) in /home/x2bingoclub1988/public_html/myurl.com/wp-includes/pluggable.php on line 1174”
and on the wp-admin page it shows up blank. I have gone to the output and looked at the code and deleted some white space or php tags that may have not been needed. but what is strange is that is just started to happen and the site has been live for sometime. no new plugins have been added or changes in the code.