1 Peter 2:23-25
23 When they hurled their insults at him, he did not retaliate; when he suffered, he made no threats. Instead, he entrusted himself to him who judges justly.
24 He himself bore our sins in his body on the tree, so that we might die to sins and live for righteousness; by his wounds you have been healed.
25 For you were like sheep going astray, but now you have returned to the Shepherd and Overseer of your souls.
You have faith
Do you notice how sin, sickness and disease were all taken care of together. If you can believe Jesus to save from sin and bring you into a relationship with the Father then there is no reason not to believe Him for the healing of your body.
The fact is, you received healing for your body at the same time you received your salvation from sin. You may have just not realised it.
The truth is that Jesus washed away your sins and healed your body at the same time with the same blood. The faith you used to receive your salvation is sufficient to receive your healing
Read 1Peter 2:24 again and notice the two things mentioned here that Christ's death accomplished. God does not want healthy spirit in sick bodies. He came to heal our spirits and our bodies. That is what salvation is all about.
God created our spirit, soul and body and He heals our spirit, soul, and body. - 3 John 1:2