Will my son and I ever come together again?

We have been estranged for about 6 years now. He is 43 and has decided that he just has nothing to say to me and wants to be separated from each other. He didn't have a very good childhood. I did the best I knew how. I was divorced when he was 12. It was extremely hard for me and his 10 year old sister. I am heartbroken over this. I want my son back in my life. I have written him letters and no response from him. He was adopted by me and my ex husband when my son was 3 months old. He was supposed to be adopted by another family but he got sick and so he wasn't ready yet so that coupe got another child. His birthday is 7/21/70 Thank you