Ok.
First of all, it is God the Fathers Heart that all are healed.
There is an erroneous belief in the church today that because a prayer doesn’t seemed to be answered it means He allows something bad to happen, even though He could stop it. This is wrong. In fact, He is constantly declaring good for you and your loved ones though His Son Jesus (Hebrews 7:25 , Romans 8:34). Yes, bad things happen, but scripture and the Saints teaches us that He can and does bring good out of bad situations, but is never the Author of them.
I also want you to know that God doesn’t answer prayers based on whether you are good or not. The reason we offer our prayers through Jesus is because He is the perfect righteous One and anything asked in His Name, He will do. Prayers are then based on His Merits, His Favor, not on us (thank God or none of my prayers would ever be answered).
Having said that, there are things that can prevent the answer to our prayers from getting through. Satan is one of them - look at how the disciples couldn’t evict a demon from a boy, only for Jesus to say that these things can only come out by prayer and fasting, now I am not saying this is your problem, I’m trying to make the point that the devil can and does resist our prayers (also read the book of Daniel, he had to wait three weeks for an answer to his prayers for the same reason).
Another is sin in our life. Again sin doesn’t prevent us from getting an answer to our prayers because we ask in Jesus name, but it can block us from receiving that answer.
Finally, it maybe that your son’s condition is not a physical issue. I have seen and worked with many people who have had physical symptoms that were rooted in psychological, emotional or spiritual issues. Once those issues were dealt with through prayer and the action of the Holy Spirit the physical symptoms disappeared.
Has anything traumatic happened to your son?