Technically, you are still married, so I would say that any sexual activity is cheating. But whether there is a legal component to it, I don't know.
Sometimes, a person has to lose everyone/everything before they realise they have an addiction. Perhaps your withdrawing completely from him will start that process, and you can have the space to think clearly.
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim