Prayers for healing that begin before one fully considers God's reasons for healing often miss the mark and create false expectations. And those invariably lead to frustration and disillusionment.
Jesus's brother, James, tells us that when we ask and don't receive it is "because you ask with wrong motives: that you may spend what you get on your own pleasures" (James 4:3)
God wants to be in an ongoing relationship with you. Healing is to facilitate that and draw your spirit toward Him. If you seek healing only to enable you to pursue your own selfish agenda, why would He bother healing your body. Remember gambit's, pledges, and bargaining's don't work with Him and remember he knows your every thought and what is in your heart. So disingenuous prayers are worthless.
Even genuine prayers seeking Him can be slow in coming for at least two reasons. The first is that we don't recognize God's perfect healing when it comes because we are looking in the wrong places oriented by our agenda. Keep your eyes open to what God is doing in your whole life and relationships. Healing has a lot broader scope than you can imagine.
The second is that God likes to work within the natural laws of the physical world He has created and the free will He has granted us ( not to say He won't overrule both occasionally). Perhaps He needs to work on the attitudes of your heart. That can take a lot of whispering into and cajoling of your spirit and thoughts----and you have to be open to listening and considering His whispers. That can take time but you can hasten the process by opening your heart to Him,