Hey there. I'm glad that you found us for support. I am really sorry that you had the reason to come find us.
Right now, just concentrate on breathing. That's all that you really should do. I'm sure that you are filled with anger, disbelief, hurt, and every other emotion that can possibly be expressed. And right now, your MILs comments should be the least of your concerns. Your WH and his betrayal of you need to be front and center. She is irrelevant, really. And it is very likely that you are using her as a sort of a whipping-boy, to redirect your rightfully felt feelings of horror, disgust, and disbelief at what your WH has done to you.
He's betrayed you. He's put your health at risk. He's put the life of your unborn baby at risk. All for a casual fuck. Not a nice way to put it, but this isn't a nice situation.
Right now, your only obligation is to yourself and your unborn babies health. It may not feel like it, but I'm betting that you're in shock. That's normal. You need to take care of yourself and your baby first. Eat what you can. Rest when you can. Stay hydrated.
Please spend the weekend reading. Up in the upper left corner, in the yellow box, is The Healing Library. Click on it and start reading. Pretty much any of the articles in this forum with a bulls-eye is also good reading from people who have been there and done that. Knowledge is power. Read up.
I know that things must seem crazy. But in all honesty, you are doing well. You have faced this straight on. Your WH has confessed to you do be aware that you probably don't know everything yet and that is common. You've gone for your STD/HIV tests. And you're talking. You are doing very well, although I know that you probably don't feel like it.
Keep coming back often for support. We're all here for you. (((hugs)))