As to why you have this problem personally, the exact reason may not be easy to determine. Sometimes we human beings so live as to bring some illnesses on ourselves. Sometimes for no known reason, they just happen. The concern now is not so much why the illness.
Doctors can often discover reasons.
1. Follow as exactly as you can the doctor's orders. Search your heart in the light of the New Testament to be sure you are a child of God as He instructs you to be. Pray for God's power and strength to help you bear the burden you feel. Live one day at a time. Don't let yourself be ungrateful and grieve over the past, or impatient and fret about the future.