Is it really just entertainment or is He looking for someone to replace me?

My husband of 25 years is addicted to online chat. He role plays a Gorian Master & Leader of a large city based novels by John Norman a world of honor and savagery, of Castes and slaves, of Warriors and Peasants. I used to work nights so wasn't aware just how involved He was with Gor, but since transferring to days & being at home with him at night I am finding out how attached he is to this chat and the ladies that are either his slaves or Free Women wanting his companionship. While sitting with him watching as he role played I became bothered by the discriptive feelings of love & lust he shared with these women. Knowing where all this chat was leading () I became angry & told him I didn't approve & felt he chose online over real with me. He of course denies it but our life is at a dead stand still & I can't get him off the computer. He is attached to a couple of women & they talk on phone too. I overheard plans to meet. What can I do to stop this madness?