I am so excited to see open dialogue about issues of this nature because we often put God in a box in which He cant deal with mental health, true deliverance, etc. The bible says "For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places." Ephesians 6:12. Sometimes we have Christians in hopes to not sound spooky dont talk about the delivering power of Jesus.
There are spiritual battles going on right now and although we cant see them at first they will manifest physically if we are not protected by the full armor of God. AliceofLegend, I heard you say that your illness has gotten worst since you have become a Christian. There is a story in the bible in which a demon is cast out and when the person it came from was left vulnerable to the attack the demon went and got 7 more worst than him and occupied the body. If you think your illness is getting worse I would suggest asking the Lord to be filled with His spirit, and know that God gives to us according to our faith, so just believe and receive!
God didnt create Satan, but Losifer the angel in heaven. He made a decision to go against God and in return was cast down. We all have a free will and decision to make. We can believe that Christ died for us or not. But KNOW that the blood of Jesus Christ covers our sins. KNOW that His sacrifice on the cross means we have access through the Spirit of God to healing, power, love, peace, and healing of the mind. Jesus we ask you to bind the enemy in the name of Jesus in his attack on our minds. We ask and receive a complete healing and believe that we can operate in a sound mind, free of ALL mental illness. We thank you in advance for your saving and delivering power, in Jesus name, Amen. May God's perfect peace and perfect love rest upon your hearts and minds!