My h has this thing that he's always had that he completely shuts down emotionally
Does he suffer from depression?
The thing about contacting the OW, is that you could end up feeling so much worse than you already do and I just worry especially as you're pregnant.
Obviously all OWs are different, but from OW forums, they will revert you to your husband.
Or tell you you're making his life a misery or horrible things like he has to think of her (OW) when he's having sex with you.
A lot of BWs have really regretted contacting the OW...but some have for more truth out of the OW, than they did from their H.
At the end of the day, it's entirely your decision whether or not you contact her.
If you do, prepare what you have to say or ask in advance.
Think about why you want to contact her. Is to ask questions? Is it to inform her that you're pregnant? Is it to tell her to end the relationship with your H?
On the last question, she could simply say your H is quite capable of ending the relationship if he wants to.
If you contact her and let her know you're pregnant, then she contacts him... he'll probably just be so angry that you've done it and ignore you for even more days.
You need to stop giving him and her the power to determine the future of your marriage.