exp has got current gf pregnant

[oscarthegrouch]

and I feel really upset about it.

Not because I have any feelings for him, but because ds will have a brother or sister who is nothing to do with me.

I am being irrational as its none of my business so why am I feeling so upset?

Don't know, but I think I would too. Think it's the sibling business. And maybe that, even though you and your ex are finished, he's part of those special memories when your dcs were newborns. And maybe the thought of him doing that again with someone else somehow tarnishes the sense of nostalgia???? Because you're not involved. Even though you wouldn't want to be with him still.
Am probably making no sense.

no makes total sense. Its hard them acting like a perfect little family (she has a ds) and theres only me and ds at home. I cant give him the same family life iyswim

I'd be devastated quite honestly and it's one of the reasons I stayed with XP as long as I did. I think its entirely normal to feel upset and I really feel for you.

thank you, i've began to come to terms with it, as well as I can. It's life i suppose. I would feel so much better if I had met someone else

Chances are good that you will, meet someone else though.
The odds are also not best placed for them though (unless they get married which up it a bit).
Don't blame you for being upsset, it's a horrid no win situation at the moment. Maybe give it time-10 years and the children will be their own people and what seems important now will have changed?