Should I tell him that he is the father of my child?

Okay, so 7 years ago, i had my boyfriend for 8 years. He's a doctor and I'm a nurse. And my other friend is the daughter of the owner of the hospital. Then, there was an exclusive offer to work abroad for me. I thought of it and decided to go though my boyfriend is begging me not to. I realized that I was pregnant when I'm gone. So, after 2 months, I went back to tell my bf. I was surprised when I had known that he is now engaged to my friend. And I tried to hide to him that I'm pregnant. I told him that I had a bf on abroad coz i don't wanna mess up their relationship. after 7 years, my son keeps on asking me who is his father. i told him it was working abroad and asked me why he isn't calling us on the phone. i cried sometimes because i feel sorry for my son. then 1 day, i found out that he has a heart ailment and can only leave his life for 6 months and he needs to die after that. i want to give him a father before he dies. then my friend suggested to me that her husband an my ex bf can be (just for my son) at first, i tired to refuse bcoz we had our past but then whenever i see my son, i just can help it. so i said yes. then my ex had to live in our house and we tried to act like a couple. after 2 months, i realized i still love him. then we had a secret relationship. after 6 months, my son did die. at first, it's very hard and now, my ex had to leave me too because her wife needs him. should i tell my him that he's the father of my dead child? i know that he loves me too. but i don't know if it will turn out well bcoz i want to avoid him now and move on bcoz his wife is pregnant now.