Trees - it's difficult, and all kinds of horrible as unfair. Of course, it is.
I did want to add something, though. You know how you said that you still loved him, and wanted to but didn't know how to work through this... I think this bit is important. I think not knowing how to - is the driving force here.
You, more that any of us - given your job - know that people lie. And for all hosts of reasons.
He didn't admit to everything right away. But you must have known that.
And - despite how MN sees men - all b/w - it is possible that he was feeling guilty and terrified of ruining any chances with you. And, despite you saying that you wanted to know - he didn't believe that you can take it and still want to try to fix it.
Mind is an interesting thing. It can make up or justify pretty much any decision we make.
If your feeling was that you wanted to forgive and work on it - you would have thought - does it really matter if it was once, twice or three times? It happened, all that matters. And now we need to move past it.
But, because, as it seems to me, I don't think you want/can actually work on it and try to move past it - (and with a baby due any moment - OF COURSE you are not in that frame of mind) - but given that - your mind looks at this and reads it to justify what you want to do.
I am not questioning your decision, just pointing out that there is more than one way for looking at this whole mess.
Ans, in the end, only thing that matters is what you feel you want/need to do.
Good luck