Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
That error occurs because your code, or your WordPress configuration and features, exceeds the memory allocated.
1. try logging Off of every WordPress login you have running, everywhere. And restart all the computers that a WordPress session was found to be still logged in on, after logging out of each session.
(How to tell the WordPress is still logged in? try to do WordPress work without logging in first.)
2. Think back as to what you may have added most recently, and reverse what you added if possible.
Then you may need to contact your web server, and have them revert or Restore your site to its last-working state. The Web Server provider, is the co. that hosts your WordPress site's files. Have them restore the full set of files in your account, or in your WordPress site, to the status it was in before the problem with logging in and the memory error, before whatever you added to it last, and then it should be capable of being adjusted further... into a state in which it won't be near memory errors.
Let me know how it goes, or if you need further advice on details.