threats to keep son?

And you're NOT talking to a lawyer about this? Do you want to hand over your child?

you could try talking to a lawyer about it

Get a lawyer and go to court to get a custody agreement issued and signed by a judge

No judge will ever grant sole custody to a father unless there is irrefutable proof the mother is a danger to the child. So don't listen to his threats because unless you have left your kid home alone with no food and a loaded gun while you were away on a 2 day drug binge, there is now any judge is taking away your custody

And with a court order, he sees the kid on the days in the order. He can't just tell your kid to come over whenever. He will have his set days and that's it

File a restraining order on him. I don't know if that would help. Maybe find witnesses to get your son to live with you. Such as your mom can also help as a caretaker. Maybe tell your ex husband that he can allow your son to visit him but that you want custody of him. What did your son say about this situation, it must be very hard for him. If you live 10 minutes apart then that's good that your son can see you both.

Do you have any proof of your ex husband as being incompetent of caring for the child, such as alcohol, drugs, mental issues, anger issues, that might be one way of you wining custody over him. Good luck

I suggest you consult an attorney who handles family law and custody issues. Your son's dad would have to prove that your are an unfit parent.

If you live in England you can take some comfort from a story in the BBC Radio 4 serial, 'The Archers', which dealt with a problem similar to yours in some respects.

There will be people who can advise on custody arrangements. They try & act in what they see is the best interests of the child. A difficult job for them because one (or both) sides may not present a totally honest picture of what they're really like.

If you're so close it may be possible to arrange an amicable 50% each split. Compromise and co operation will be needed from both sides if this is to work.

Does your son have any preferences? These will need to be considered too.

I seriously hope you & your ex aren't abusing each other mentally or physically, other or running each other down, or constantly criticising each other in his sight or earshot. If you are this will cause him a great deal of stress, and it may give him emotional or relationship problems himself when he's older.

I would suggest you contact your doctor first, or you could ask at your library or citizens advice bureau. Or your local council. Or just do a web search, maybe something like childcare advice after marriage breakdown, or something like that.