Welcome to BPDR

I know how scary it can be to face the thoughts -- it's like they could take over if you let them. And if you did let them take over, what would it gain you? Would you gain something different and/or better if you fought the thoughts & prevented them from taking over?
Sure, it's a real possibility but it's only a possibility. It's not a certainty so don't treat it as such, if you can help it. And even if it does come to pass, who's to say that it's a forever thing? Or that things will spiral downward as a result? It could be that him having her will give you the space and time to focus on getting your own stuff squared away so that you can develop a healthy mother-child relationship in the near future.
All sickness ain't death.