"If thou wilt diligently hearken to the voice of the Lord thy God, and wilt do that which is right in his sight, and wilt give ear to his commandments, and keep all his statutes, I will put none of these diseases upon thee, which I have brought upon the Egyptians: for I am the Lord that healeth thee." (Exodus 15:26)
Has the devil ever tried to put you under condemnation by telling you that it's contrary to the principles of faith to use doctors and medicine when you need healing? If so, here are some encouraging words that I believe will help you put your heart at rest.
It is God's will to heal you. That's the first and most important thing for you to understand. If your faith is strong and you can believe the Word without wavering (regardless of what circumstances or symptoms come against you), then you'll be able to receive that healing by faith alone.
But that kind of faith takes more than just hearing a few sermons about healing. It takes a deep personal revelation of God's healing power. So, if you haven't yet developed that kind of faith, the doctor is your best friend.
If you're not certain whether your faith is strong enough or whether you need a doctor's help, follow the instructions of the Apostle Paul (Col. 3:15) and let peace be your umpire.
If fear rises up within you when you think about doing without medical help, then go to a doctor. And go in faith! On the other hand, if you have a sure confidence within you that healing is yours strictly by faith, let your faith do its work and receive your healing directly. Whether or not you go to the doctor is not the issue. It is what you do with your faith.
Either way, you can rejoice knowing God is working with you, meeting you at the level of your faith. Thank God for your healing--however it comes!--and do not let Satan put you under condemnation. It is none of his business.