You are not having a tantrum. You have said it yourself that you know what you have to do but you don't want to. Hunny, I'm not one to say this ( I've been through stuff too) but think really hard about how much happy you have. If you want out now is the best time to do it, not later.

>>>He says that I should understand that he was with his wife for 20 years and that he cannot just let go and that he is being nice and helping out...<<<

My DH was married to his ex for over 20 years, and had no problem making a clean break when their marriage ended. There was no hanging on, no spending time at her house, no paying the mortgage on where she and her mommy lived, no jumping, no going back for seconds. Just...nothing.

If you don't want to break up with him, be prepared for her to come first and to not truly have him in your life as a partner.

I don't understand this post. You are having an affair ( which is wrong) and she is fighting for her marriage ( which is right). You are not the victim. She is. Get off you moral high horse.

He's not a nice guy. He's taking advantage of you. You and his ex are allowing him the pleasure of sleeping with 2 women without needing to hide and lie.

If there is no divorce decree, it is not over. Have you even seen a draft of the judgment?

Is he divorced yet? If not, has he talked about actually going through the divorce? If not, it really doesn't look like things will change. If you don't like where things are at now, then it most likely won't change anytime soon.

My DH left his ex-wife for his now ex-girlfriend. They "dated" for a year while he was still married and living with his ex-wife. He slept in the guestroom when he was home, but stayed at the girlfriend's many nights too. I never would have tolerated that situation, but the girlfriend was ok with it. Everybody is different. After that first year, the girlfriend decided to buy a house, and that's when DH moved in with her, and BM filed for divorce.

I personally am glad I met DH when he was living alone and not attached to anyone in any way. I get the feeling that many men will not go through with divorces if the women in their lives let them get away with it all.

This man cannot let go of his wife and you will always play second fiddle to her. Spending time with his kids does NOT mean he needs to be emotionally attached to his wife, and it sounds like he is using that as an excuse to hang onto her. So what if they were together for 20 years? Lots of people walk away from long relationships/marriages (including myself) and are quite capable of forming new relationships while maintaining a relationship with their kids. You deserve a man who can commit to you 100% and he never will, and as someone else said he's having his cake and eating it. You're providing somewhere for him to "stay", sex and all the rest of the perks he gets at your place but he knows he can run back to her whenever he wants. Maybe they are still sleeping together, maybe they're not but whether he's having a physical relationship with her or not he will never be fully "yours". You don't want to waste your life hanging around waiting for him, you deserve better than that. It will be hard but you know what you need to do, and then hopefully you'll find a nice guy who makes you his number one.
Good luck