I've been with a married man off and on for 5 1/2 years... I have tried desperately to leave him but I'm addicted to him... everything about him... we are a perfect match made in sexual heaven! He gets me and I get him... I don't want him to leave his wife

And... what is your question for us? What to do? First thing you can do is stop calling it an addiction. You are having this affair because you want to and have chosen to, not because of your brain chemistry. If it bothers you, stop cold turkey and turn off all contact. Change your phone number, delete all accounts, don't answer calls or doors. Thousands of people do that every day.

So keep cheating with him, watch him leave your bed and go back to hers,

I hope at least he is paying your rent and other bills. The mistress is suppose to be well supported

So what's your point?
You're not addicted you are stuck in a sexual rut.
When you are really tired of it, you will stop.