God bless you. You took care of that child even though it was so very painful for you.
I am positive that the adoptive parents are remembering you today, also. Maybe your son is not old enough to yet, but he will some day, too.
You can write him a letter and send it to the birth parents or adoption agency to hold for him some day. It really will mean everytbing to him when he gets it to know that you thought of him all those years.
May the Holy Spirit comfort you. I prayed for you, in Jesus' name, amen.