Your sitch sounds so similar to mine. It sucksucksucks sitting in the same room as them and watching them texting the OP while we sit on the couch and fight the urge to ask them to come watch the movie and cuddle.
I know in my sitch I've talked about how H texting what I perceive as an OW makes me feel badly. He blinks, confused.. frustrated... then angry. Then the comments begin, like "What, am I not allowed to have friends?" or "You need to make some new friends, I have." or "I am sorry that this is hurting you to see... I'll just go over to her house again." or... etc, etc...
Sigh. I've learned not to open that can of worms. He's going to talk to her come hell or high water.. and am I going to stop him? No, I just drive him further away when I bring it up.
And I totally get what you mean about "how can someone she's known for 2 weeks usurp my position?".... I asked my H, point blank, a similar question. I'm known him for 16 years, 14 of them together... I have been through so much for him, done so much for him, held his head when he cried, picked him up when he was broken... for 14 years... and this new friend you've made and known for 2 months means just as much to you? He answered me with a yes.
Dear goodness.... welcome to the crazy train. They say don't believe 100% of what they tell you and 50% of what you see. It's hard when them seem so convinced tho'.
Lol... don't suppose you live anywhere in Canada, do you? I'd love to bring my kids (S5 and D4) over for a playdate with your little one.
You're doing the right thing, I think. The texting is going to continue whether you're in the room or not... so remove yourself from it and GAL in another room.... whatever you can find the emotional energy to do. Take a bath, read a book, run on a treadmill, learn guitar... just get away from the EA. Put yourself first... even in small ways, if that's all you can do at this stage (I'm still learning how to do this, all over again.... it's funny how we forget)... your son needs a stable center spoke in his turning bicycle wheel world.
I'm riding the same crazy train you are... so similar. It stinks... and this is my second time on the train. Only way to survive is to open the cage door and let the WAS out on the journey that they are intent on taking without you.