Oh tumble, I read your first posts and posted a bit, haven't been back since now, and now I feel this urge to take you in my arms and give you a big hug. You so remind me of myself at your age. I haven't been in your situation, but I too was so eager to believe all the things my partners told me, all the things that really didn't make sense but somehow always managed to come up with reasons that I couldn't deny and because it suited me to believe them, I did. It ended badly each time, betrayed, heartbroken and totally confused as to why they had treated me the way they had. It was always the same thing, they really really liked me but...
It took me 10 years to finally learn to recognise the type and I'm afraid to say that the father of your child to be born is showing all the signs of being a professional liar and probably some sort of two lives, if not being with her, making her think that your relationship is not the one that you believe you have with him.
The whole thing 'I went home at 5pm, fell asleep, didn't hear the phone, I'm so sorry but miss you soooooo badly' is so classic, it makes want to go to him and smack him in the face. Believe me, men who are committed never act like that. Even if it was true that he was scared to not being able to see his kids if he didn't do as his ex asked, even if it was true that he went there under duress and because it's the only way he could see his kids, a NORMAL father to be and loving partner would have been on the phone the second he left her house, saying how he realised that the situation wasn't right, that he was going to make it different next year, asking you how you were and that he was sorry to put you through this' and even if he was poorly, he would have still called you to tell you so and tell you that as he was feeling rough, he would want nothing more than to be cuddled up with you.
No caring man would put his partner through what he has put you through and then just go home, fall asleep, somehow not being woken up, and only then think 'oh yeah, I remember I have a partner who I've put in a very upsetting position, who has accepted it because she is wonderful, yeah, I guess I should call her now that I suddenly remember she exists'.
I'm so sorry Tumble but he really is full of s... and only getting away with it because you are clearly a very nice person, who only sees the best in everyone, and who can forgive easily because that's what you are supposed to do and showing your anger is not acceptable. He knows this and uses it to his favour.
I hope you go back and tell him what a F.... he is just as you rightly told him in your text, that saying that he fell asleep because he was feeling so poorly is not even close to being a good excuse and that he knows he should have been on the phone the second he left the house. Let your anger guide you, sometimes, it knows better and in this case, this is exactly what you ought to be feeling.