Tell him the truth. Your physical body gets broken, gets sickened. There's no denying that when it has happened, and it's not a statement of great faith to say that you aren't when you are. There's a difference between speaking "negative confessions" and speaking truth.
Negative Confession: "Oh man, I'm gonna get sick from being out in this cold weather too long."
Truth: "I got a sore throat from staying out in the cold weather too long."
Bear in mind, a negative confession can bring about its truth. What we bind on earth is bound in Heaven, and what we loose on earth is loosed in Heaven, being it healing or sickness. It goes both ways.
I heard it explained this way before, too. God will use whatever we need to grow our faith into the manifestation of healing. Ever hear of a placebo effect? That's faith that medicine is working. I know several great men, Brother Kenneth Hagin Sr included, who after being healed from his disease, did not need Doctoral or medicinal healing, but rather knew the order of authority and that if his Spirit was submitted to God, then it would reign over his body and he could by faith recieve healing if needed.
I am a Worship Leader, and I am very keen to pains and such in my throat, vocal areas, and my hands and fingers (sing / guitar). When I even notice something that would feel like it is going to "lead" to a certain outcome, I start immediately building my faith against it by speaking positive confessions.
The truth: my throat is starting to hurt.
The Positive Confession: I thank you God for providing the healing I need to continue in the ministry which You've called me. I recieve that healing and if there is somethign within me that is hindering me from recieveing, I pray for sensitivity towards Holy Spirit to show me what it is, so that I may submit that part of my life to you, and receive the fullness of what you have already done for me."
This is how I do it. Others may view differently.