Postdoc overwhelmed by incomplete work
This is a well known problem - and depending on your personal situation you should consider getting professional help by a psychologist. It's not a shame and it might prevent further harm. They could assist as well in creating a step-by-step program.

If you are willing to handle the situation by yourself, you'll have to do "a few" things (which are a lot to do!):


Learn to say "no" to specific tasks. Do not accept any new assignments unless your papers are done.
Figure out, why you are procrastinating - your mind has a reason for it and you should figure out what it is. 
If the overall workload is too high, cancel some things forever. Eg. decide not to submit one of the "old" papers. How does this thought feel? Better or worse then the actual situation? 
Go on step-by-step. Focus on finishing one of the old papers. Submit it. Take a break! Choose the next step of work.
If needed, be disruptive. 


Take a longer break (e.g. 4 weeks of vacation)
Move your whole inbox to a subfolder "old" and never ever look at it - important mails will be re-sent.
...

If you are having a good relation with your supervisor(s), involve them in the process.