Hello sorry about so many misunderstandings, I am not one to give advice, but let me see If I can help. Faith has alot to do with it, but there are other things in our life that can hinder healings, such as Our walk with Christ, if we are living in open sin God may not heal us, also the third thing that I know that may hinder a healing is that as the Blind man in scriptures, they asked Jesus who sinned the man or his parents seeing that he was borned blind, Jesus said neither had sinned. that the man had been borned blind that God might get the glory this day, and the man recieved His sight, also satan can rob us of a healing , see A healing is different from a miracle, I go to Church the Spirit is moving, it changes into a healing service, I go up because I been having bad headaches the preachers anoints me, prays for a healing, I go home then to bed the next morning I wake up my head starts hurting , then satan steps up says see You didn't get healed, you are still hurting, steals my faith, the head aches come back.
Jesus said to some that were healed "Go and sin no more" told one that if they did sin that the illness would come back stonger than it was. I am not saying that you are living in sin, just that this could be a reason why people don't get healed. sorta like you go to church you get prayed for , then you leave Church and go jump into bed with your Boy/girl friend, and it was God's fault you didn't get healed. so yeah faith is one thing , but many others factors may hender us from a healings / miracles. you said 20 yrs I think it was wiggles worth dad that was in a wheel Chair believed that he had received a healing from God one night at church, would tell people after that night that God had healed him and that he was coming out of the wheelchair, and 26years later he did just that, He walked away from his wheel chair
\ let me share a little story about faith, back when people depended on farming there was a town that was experiencing a drought, it was real bad, things were done past drying up they were already dried up, the town call for a pray meeting they were going to pray for rain, so all the people came together for the prayer for rain , But only one Little girl brought her umbrella. now thats faith asking God for something and expecting something From Him !!!!
Hope this has helped in some small way, I have a friend with ms.