Agree with the advice you've already been given. What you described isn't piecing so much as a mooch that has probably overstayed his welcome elsewhere and feels like bouncing back into your life long enough to sponge off you for awhile. That's the harsh assessment of the situation. But really, he isn't remorseful about this. He feels he has an open door to return whenever and however he pleases.
I would make your feelings known rather than be resentful. Let him know it isn't that easy. If you aren't ready for him, tell him you don't want him back now, and possibly never if he can't see how to act like a responsible husband and father. He should be winning you back...not just being taken back. Your resentment is your self-esteem telling you that it's taking serious damage by letting him come back so easily.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
