Hormones are going to get me in trouble

Lately I swear my temper has been at a breaking point when it comes to my ex husband. He was abusive and is overall just a serious a-hole. Normally I'm able to brush him off but lately I'm ready to lose my religion. We share my two children. I told him about my pregnancy in order to get him to sign paperwork so my children and I can move to Texas to be with my fiancé (father of the child I am carrying) and all he keeps saying is that my pregnancy might not even be viable, and hinting towards the chances of a blighted ovum. How do I keep calm and brush him off again?