To suggest that Paul's thorn in the flesh was an illness is speculation, he doesn't actually say what he is referring to.
To say that the failure to procure your healing indicates a lack of faith is a little too simplistic. It is infinitely better to die sick in Christ than to die whole without him. To rach1370 I say, how do you know God will not heal you? Yes, he has not healed you... yet. Yes, you have asked and, as I understand Jesus' words and actions, asking presupposes faith. Now you believe you have received an understanding from God, and that is good, and it is good that you live by it; but you have not reached that point in your life where God cannot heal you.
Concerning cally's reference to the will of God I agree, yet disagree. To pray for healing is to pray in the will of God Jesus taught us to pray, "thy kingdom come, thy will be done," and later testified, "if I, by the finger of God cast out devils then the Kingdom of God is revealed among you." When we pray for one another to be healed, and it happens, it reveals the power and authority of God through Jesus Christ. I would that we saw more of it.
Take another look at Hebrews 11 concerning faith. Faith is not the ability to always get what you want. Faith is the attitude of obedience to God no matter what your circumstance, but this faith has the infinite ability to receive all things from God. Now he that said, "believe in me and have everlasting life," also said, "believing, go into all the world and preach the gospel with signs following." It is obedience to heal the sick, cast out devils, and do all things in the name of Jesus Christ.
Let me just say that it is our expectation that often hinders us in seeing the glory of God revealed. This is what I have seen in the denominations and factions. Where there is little or no expectation for God to show his glory in this way they do not practice the laying on of hands that others may be healed. Rather there is debate and confusion. If you do not obey the instruction of Christ you cannot receive the benefits he has promised by them.
I have right now, rach1730, asked God for a gift for your healing that you may find a new rejoicing in Jesus Christ. This is what I do. If one is sick I ask God to heal them -- to give someone close to them the absolute assurance when they lay hands on them they will be healed. Then I wait to see it done in the name of the Lord Jesus Christ.
Since I know that God is no respecter of persons I always ask myself, why should I be healed on no less than 5 occasions and another never experience it once? That is my story and why I cannot accept that God has no intention of healing anyone.
Read the gospels and see how long some were sick before they were healed -- 12 years and more. God's word is coming to heal you, and indeed has already arrived. Do not despair.