My husband and in laws are not giving me my child custody

I had filed divorce by mutually. At that time it was mentioned that my son will stay with me. But his father and my inlaws are not allowing it right now. They are ready to give me child custody but after divorce they want to keep in touch like they want to maintain relations with my son but i dont want that. If i want to think about my second marriage it will affect on that and on my sons mind too. I want my child custody what can i do? Will my husband interfere in my further decisions? Should that another person with whom i m going to marry will be able to adopt my child legally? Plz suggest