What a complete a'hole.
If his feelings have gone then that is fair enough, I mean, sometimes you do fall out of love with someone.
the thing that he needs to think about is that you are pregnant with his child and he needs to show some backbone.
If he wants you back in a week then great, and I hope you manage to work it out.
If he doesn't then you need to establish what he intends to do about his children.
At the end of the day, they are the most important people in this situation.
Regarding keeping the baby, do you have support that you can rely on with childcare or having someone there for you?
Keep pride in yourself, it is his problem and you haven't done anything wrong.
Definitely don't beg for him to come back or he will use this to his advantage. ideally, he should be begging you to take him back.
Don't stand for any crap from him and set out some rules if he does decide to not come back. If he comes back then he has to show that he is committed, especally if you decide to keep the child with him.
Good luck though, be strong and keep your chin up.
K x