<human>: My fiance enjoys roleplaying on a website that involves IRC chats. It's something he's indulged in since high school, and while I told him that I was able to deal with it in the beginning of our relationship, a few months later I let him know that it makes me incredibly uncomfortable and prefer that he stop. He did, for a short time, but would press me from time to time, suggesting that I don't trust him, and remind me that it's simply the story. 

After considerable pressure I caved again recently and let him return. When he's on these sites he often spends hours crafting the ideal response, while remaining short tempered with me when I interrupt him. Things in our relationship have been very rough lately, and our marriage has been delayed due to circumstances beyond both our control. We had a pretty bad fight about this last weekend, where I told him that I believe that cybersex is, quite simply, cheating, and he feels that it's just his porn and I don't mind him looking at porn. I know this man is faithful, and would never cheat on me, but it's like a stab in the heart when he roleplays with strange women, particularly because I've offered to do so with him. He doesn't want me there. 

This issue is crushing my self esteem, I know I've put on weight, and I'm working hard to take it off, but I feel undesirable and rejected. I've told him plainly how I feel about it, but he told me that I have to -tell- him to quit. I have a hard time demanding that a grown man do anything. Am I completely overreacting, and is there a reasonable way to handle this?

Could you distill the essence of the text into 1-3 sentences?
<bot>: Fiance likes to erp via IRC. He says it's his porn fix, but he's very flirtatious on these sites, it's destroying my self esteem and I feel it's cheating. Suggestions?