You are working yourself up into a bit of a state. Have your lunch and force yourself to do some work. Turn off your phone if you can.
Do not text him.
OK, looking though your messages:
It would be very silly to meet him for coffee when your emotions are in the driving seat, so to speak. You have had an emotional high over the weekend and you are allowing it and encouraging it to continue. Like onandup says, it's like a drug habit. Just because it is making you feel good today, doesn't mean it's good for you long-term. It could (and would) make you feel like hell tomorrow.
You are not in the midst of a kind of madness and I don't think it is helpful for you to start thinking that way. You are not mad. You are a sane woman with choices and options, and you are going to have to deal with the consequences of those. You are already dealing with some of the consequences.
What if you one day find yourself having to explain this whole period of time to your DP? How would you explain giving yourself permission to continue texting OM, once you had decided he was not good for your relationship with DP? How would you explain giving yourself permission to meet up with OM?
Only you can answer your question about whether you should try to rescue your relationship with DP.
I think it is very good that you have the session booked on Friday. My advice is this: use the session to make it crystal clear to DP that your relationship is in crisis.
Be as open and honest about your true feelings as you can. I'd suggest telling him that you have found yourself having feelings for another man, and how much this has alarmed you with regard to your relationship.
Right now, you are in a position where you can ask your DP to examine his behaviour and explain how much it has pushed you away. There is a chance that he will be willing to work on it, if you make it clear enough what is at stake. There is a balance - even if he knows that you have had feelings for someone else, you can also show him that you were more concerned with saving your relationship with DP. There will be work to do on both sides and - hopefully - willingness on both sides.
If anything more were to happen with OM - even just meeting up - I think you would completely change the balance. You would make it so that any honest discussion with DP would result in him feeling terribly hurt and you feeling terribly guilty. Would he be so willing to work on the behaviours that upset you? Would he find it easy or even possible to be more loving towards you?
I'm sorry, but I think that if you reconnect with OM now, you are closing the door on your DP and locking it.
You need to be able to answer your question. But there are two of you involved in this situation - you and DP. So I think you should be asking him the question too. Can you face telling him what you said above?
"If you and I didn't have young kids together, I would have left you 6 months ago. Given that we have children together, should we therefore do absolutely everything we can to rescue this relationship?"
You will notice that I changed the 'I' of your words to 'we', because I do believe it has to be both of you, working equally.
You have a counselling session booked because you are in need of help to make your relationship work. So be honest at the session. Ask for the help you need. Explain the full extent of your feelings and fears.
This is going to take enormous courage and strength, both of which I know you have. But please don't chip away at those qualities by continuing to contact the OM.
Here's what I think you should do this week:
- Delete the weekend's texts from OM. Pretend it never happened. Don't text him to let him know that you are breaking off contact again. Just do it.
- Whenever you start thinking about OM, grab a piece of paper and write down the things that you want to achieve from the counselling session with DP. Write down your thoughts about it. If OM comes up in the course of those thoughts, write about him as a symptom.
- Go to the counselling session on Friday with a view to it helping you to decide whether you want to try to make things work with DP. You will be going there 'clean' in the sense that you won't have texted OM all week and you will have been focusing your energies and thoughts on DP. So use that time and space to lay it on the line. Be kind, but honest. Talk about how DP makes you feel and about the doubts and longings you have been experiencing.
That's my suggested three-point plan!