Hi OP.
I’ve read your previous threads and this one, never replied because you had a lot of people doing so and to be honest, I was unsure if I could say anything helpful just because I found it so hard to believe anyone could be so completely passive in the situation you describe. That may well be very unfair of me, people react differently and I realise that.
That said, I think you need to start being honest with yourself about what you want to happen here. You seem to keep looping round the same circle, constantly focusing on the small details - why keep a number? Why not block? Why use that exact turn of phrase? Why did he say x to her and not y? Why did he not contact her for such amount of time? Has he told her you’re pregnant again? What does that mean? Etc etc etc. I think you’re trying to distract yourself from the bigger picture or thinking that if you can just somehow ‘crack’ the answer to whatever tiny fraction of this whole mess you’re obsessing about this time, then you’ll be able to fix it all somehow. It won’t work.
The truth is he’s not stopped contact, he has no intention of stopping contact, and he wants her. Whether he’s making outright declarations of love or ‘being coy’ to keep her hanging on as you put it, he’s acting in a way that puts an ongoing relationship with her above your relationship and ahead of any chance of salvaging your marriage.
I know you say you don’t want to think about it yet and want to keep things calm until the birth but seriously - how much calmer is it going to be with a newborn? It will no easier, arguably harder actually, to raise this when you have TWO children to run round after and you’re trying to establish feeding and sleep deprived and recovering from birth etc. So why exactly are you holding off talking to him about what you know and the latest you’ve found out? Are you hoping it will all just go away if you ignore it? Are you hoping he’ll fall in love with the newborn and realise what he has to lose and stop contacting her? Because if your existing son wasn’t enough for him to do that why will this be different? I think you need to be honest with yourself about what you’re hoping for here and how realistic that is, because if you’re hanging on to some kind of fairytale post-birth reconciliation where everything goes back to how you thought it was at the beginning- it’s understandable but I’m scared you’re setting yourself up for a massive fall.
You’re not happy together - this isn’t an honest, emotionally intimate and fulfilling relationship for either of you. If you want to stay together despite that then fine, that’s your call and nobody can tell you what to do. You can stay married, focus on effective coparenting and keeping up appearances and stop expecting any kind of honesty or fidelity (emotional or otherwise) from your husband. Plenty of people do it OP and I’m not judging. BUT - the huge caveat here is that you then need to stop checking his phone, stop caring about who he’s contacting and stop letting it affect you. As pps have said in that situation you’d need to focus on yourself, building your own life up and finding other sources of emotional support than your husband, who doesn’t seem to be able to offer you that.
I know what you really want is for him to give her up altogether, fall back in love with you and recommit to your marriage and family. But he’s shown time and time again you can’t have that, he’s not prepared to give you that, it’s not in him. So stay together or don’t, but be honest with yourself and try to get into as strong a position as possible (emotionally, financially, physically) with a life that doesn’t solely depend on him - then at least you’ll have options and won’t keep getting blindsided and devastated at every turn.