You poor love. When you are in less shock, you might see what other readers might deduce from your posts:
This is not your fault.
You said you didn't trust him because your gut feeling is that he has got someone else on the go at the moment. Given his history, this is a perfectly reasonable statement to make. Someone who was "over the moon" to have been given a second chance would have taken you in his arms and reassured you that nothing is happening with anyone else at the moment. He didn't - he walked, saying that he didn't love you and blaming you for a lack of trust. My guess is you were right - he does have some other love interest at the moment. He won't want to admit that, so is deflecting the blame on to you for what is a perfectly reasonable lack of trust.
Why on earth would you trust him?
Instead of reassuring you and committing to your marriage and new child, he has whiled away his time at the pub.
This is not about you, it is about him.
Hard as this is, your best coping mechanism now is to take him at his word and tell him that you have accepted your marriage is over. Get that legal advice and refuse to collude with his version of the truth.
You have coped before without him, you will again.
You will meet someone in the future who is not like him - and that will make you realise that this isn't about you at all.