Im willing to bet most of that is your unbelief... It has nothing to do with lack of faith but maybe a bit also with your understanding, you have faith but unbelief is an independent entity separate of God's will
to heal you. Faith is in complete agreement with God always, faith is agreeing with God.
2 Corinthians 10:5 5 Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ;... This is your mind when you aren't in the new man mentally, you have to just accept that what you think is wrong and God is always right. That can be hard for some but you are humbling yourself when you get into practicing this because you are allowing His ways to be magnified and affirmed/manifested through you... If your mind ain't right he can't work. Matthew 13:58 Now He did not do many mighty works there because of their unbelief... When Jesus would heal people often times He wouldn't openly tell people that they were healed, most of the time He would command them to do something first that they couldn't do and then they'd find out after. Faith is obedience by agreeing to the word... Imagine if those people never acted upon Jesus's command after being healed, for example He commands a man to rise up and walk but instead the man is like "nah my legs are too messed up Jesus, can't you see that im a cripple?." That man would never receive his healing because he didn't act as commanded but instead he chose to live as commanded to his own belief that he was still crippled because that is what he can still see, feel in the flesh rather than acknowledging and responding to a higher authority which is Christ.
Your mind shouldn't still be on that God "Can heal me" but focus on that "God already did heal you according to Isaiah 53:5, By His stripes you were healed" Faith is simply agreeing/ affirming with Gods word and work of healing you even though you may not completely believe it or be able understand how it all works, but what you need to focus on the most is that God/Christ is always right and truth even though your body and physical senses are telling you the opposite. If God is always righteous somewhere down the line someone/something is lying which is the flesh and what you must do is submit yourself by just tapping into that childlike faith of agreeing with God so that the faiths are now in agreement so it's two to one, God and you vs your flesh.
Matthew 18:20 For where two or three gather in my name, there am I with them.”
God already believes in what He did on the cross so now you have to line up with it. This is not just head knowledge like something you just learn in the moment and then skip off into the sunset, but the revelation of His righteousness has to sink in as you renew your mind and put on the new man according to Ephesians 4:23-24 which basically just affirms whatever God says. The old man just says things like "im still sick" and his entire perspective is counter-faith because he sees from the perspective of the flesh and not in agreement with God who is in spirit.
How you get there is by reading the word obviously but also praying to God in agreement about your healing and things He has already provided, you need to start also speaking as though you have those things too. Start saying that your back is healed/healthy every day even if it is on fire, in faith agreeing with God you need to start just moving it around and doing things you don't feel like doing. Healing is provided but you take it by force by appropriating it, that's why sometimes you see some christians say things like " i accept or i take my healing" when you see testimonials. Healings aren't always instantaneous like how we imagine them. I remember laying hands on a 15 year old deaf dogs ears and they didn't open till a month later, then there are some healings that happened in an hour or a day. But all in all truth is truth no matter how you slice it, God is faithful, and righteous no matter how long it takes to see a manifestation.
So yeah work on your agreeing with God by renewing your mind to what all was done concerning your healing and to Him always being right and once all of that resistance is gone you should just end up healed. It is Gods will for you to be healed and well, your healing is about His purpose and will for you and not just because you want to feel better. God actually wants you well even more than you do but His will always has to come first by us agreeing to it.