Have had counselling since leaving XP, but didn't find it that helpful, because I just didn't think to bring the issues up in the day when nothing was happening to trigger them off, if that makes sense. But keep meaning to follow up GP appointment for referral to CBT or similar for some other issues, and from what I have heard, these things all tend to be interrelated so hoping that if there is something to come up, it might come up there.
I suppose that I'm worrying about what notsorted said - that if DS finds out later he has a half brother, that might be weird for him. Or if we talk about it periodically so that it's not some big secret, but he always knows it, what happens when he gets older and says "But why don't I ever see my brother, mum?" I still take him to see his grandmother on XP's side, and she sees the other ex and her children sporadically, so there's a chance they could meet there when older but at the moment, me and the other ex would have to be there, and I'd just rather not. My gut feeling IS avoid. I'm glad you've all said the same thing!