problem loading my admin page

I have not upgraded to current wordpress? Is this why today when I went to login to my admin panel – it took several minutes and above the login I got this:

I am thinking of disabling Ajax contact form and finding another, but can you tell me is it just because I haven’t upgraded? Sorry I am a newbie to blogging.

Warning: Cannot modify header information – headers already sent by (output started at /home/handwr7/public_html/wp-content/plugins/ajax-contact-form/ajaxcf.php:124) in /home/handwr7/public_html/wp-includes/pluggable.php on line 712

Warning: Cannot modify header information – headers already sent by (output started at /home/handwr7/public_html/wp-content/plugins/ajax-contact-form/ajaxcf.php:124) in /home/handwr7/public_html/wp-includes/pluggable.php on line 713

Warning: Cannot modify header information – headers already sent by (output started at /home/handwr7/public_html/wp-content/plugins/ajax-contact-form/ajaxcf.php:124) in /home/handwr7/public_html/wp-includes/pluggable.php on line 714

https://www.ads-software.com/extend/plugins/ajax-contact-form/