Hi Hello, and thank you so much for your thread, it's not easy to post a comment yourself but your bravery acknowledges the strength of others, well done.
When a spouse cheats on you then the marriage takes another dimension, it may completely change for the good or for the worst, especially when it's done with a workmate, because many different situations need to change, you can't work together any longer and your ability to focus on achieving the work has to be readjusted.
I want to congratulate you on being pregnant but understand how you are feeling and very sorry for how you are feeling in these circumstances because your emotions come with legitimate reasons.
For him to say I'm sorry for everything can also feel generally unsatisfying so you want a written apology which he refuses to do, so this is probably what you need, but when he doesn't want to, is going to create another argument, although he may feel this could be used in a legal debate, well the fact that he has had an affair is already evidence.
I'm so pleased you are going to marriage counselling but worried that you have children and now pregnant with another one.
Have you thought about separating and by doing this may enable you to think clearer because with the two of you under the same roof maybe a problem, although I appreciate you may need additional support around the house.
I feel your sorrow.