The intention of recovery mode, just so you understand, is that it allows you to disable the running of any external code.
So you would be adding the recovery mode constant to say "Kill anything running that isnt default, and let me log in. And when I log in, disable all 3rd party so when I remove recovery mode, they are all disabled"
So
Add recovery mode constant
Log in and allow it to disable everything
remove recovery mode
You should then have access to your site again. You would then be looking for what the cause was. You can check in system logs which may give you an indication as to which broke your site, and start ensuring items are updated to the latest releases that have been sent out by the authors.