God op, I couldn't even finish reading that before commenting. You poor poor thing, I am so sorry you're having to go through that. His actions are incredibly selfish, and like he cannot hack the tough time, so has done a runner to Mummy (probably to be waited on hand and foot) for some sleep and peace. He sounds like a cowardly man child, with absolutely no thought for anybody else, but himself.
What a shit dad to do this to his dcs too. I bet if there were no dcs he would still be there. Do not let him come crawling back when the dcs are older, and things get easier. He has left you at a time when you're the most vulnerable, and need him the most; what a pathetic excuse for a man he is. Your dcs are young, he chose to have them with you; his excuses are lies because he cannot hack it. There is no coming back from this for him.
I hope you have support. Things will get better in time, it'll be a tough path a head, I cannot begin to image what you're going through, but I promise as your babies grow it'll get easier. You don't need a weak man like this in your life; he doesn't deserve you, and he doesn't get to walk back in to your life later down the line. 💐x
Just read the other woman part, this is even worse, I am disgusted. This isn't falling out of love, this is bailing and running off because he cannot hack it. You're better off without him.