Dolp - Yes, you do not need another relationship now. For now, you have to rebuild the relationship with yourself. That's top priority.
We could somewhat be in the same boat, my husband and the other woman are still together while he's doing 'surface' work of trying to win me back by acting all 'bruised and victimised'. If you are able to see things from another perspective, it's actually rather amusing watching him.
I do not know of any support groups but this is what I have done since I made the decision to walk away. I wouldnt call it advice, it's just some pointers that I am holding fast onto.
1. Set short-term achievable goals e.g. picking up a new sport, a new language, widening social network, quit excessive drinking (too many embarrassing moments after getting drunk), losing weight (haha). Learning how to drive is next on the agenda. I actually wrote them down on paper and had a completion date against each task. As you can see, there's really many things you can do.
2. Stay focused on moving on
I am making a very conscious effort to stay positive. I hung out with positive people, thought positive thoughts, spoke positive words. You know how misery loves company. It just multiplies, IF you allow it to. I made it a point to be there for other friends who are going through rough patches in their lives as well. It helps when you do not allow yourself to be consumed by your own misery.
3. Reflection
I did a lot of reflection on myself during this period of time, and I'm sure more in time to come as well. I wrote down on paper the mistakes I made, the lessons I learnt, the kind of man that I will 'run opposite direction' when I meet them in future... (ok, kidding... haha)
4. Minimal contact with him and his family members
Very important to block out all the 'noise' if you have decided on a divorce.
Stay in control of your emotions, but be kind and give yourself time to recover. I have my weak moments too but I literally talk myself into snapping out of it.
I see a happier future without him and will continue working towards that.
Cheers, babe.