Antenatal OCD and Fear of Being Poisoned?

I've developed horrible antenatal obsessive compulsive disorder which I am being treated for but treatment has been largely ineffective. My worst fear is being poisoned. I (irrationally) believe someone is "out to get" me or my baby, or believe I won't be a good mother and so they'll try to harm the baby by poisoning me. It's horrific. I cannot leave a bottle of water unattended after opening it.

Has anyone else experienced this (even in a more mild form) or any other antenatal mental illness? How'd you make it through?

I just need a little reassurance I guess. I know, logically, the thoughts are irrational. But they are hard to fight.