It is so painful to hear harsh and dismissive words from your own family, especially from a grandmother who should speak with care and love. Please know that what she said about you is not the truth your doctor has given, and you do not have to receive her words as if they define you. Jesus said that we are justified or condemned by our words, which shows how powerful words can be to wound or to heal, but the truth is what matters before God and in reality.
Jesus Himself knows what it is to be misunderstood and rejected by His own family. His own brothers at one time thought He had lost His mind and said He was beside Himself, and He taught that a prophet often finds honor everywhere except among his own people and his own household. When you follow Him, you may find that the closest hurt comes from within your own family, and He understands that pain completely. He also taught that those who belong to Him become a new family, where the bonds of faith can be even deeper than blood ties, and where older ones can be as mothers and fathers and those your own age as brothers and sisters in love and purity. You are not alone, even when family words make you feel alone.
I want to pray for your healing as you asked, and to encourage you about how God heals. The Scriptures show that Jesus healed in many different ways. Sometimes He healed instantly with a word, sometimes with a touch, sometimes by going to the person and sometimes from a distance, and at least once the healing was gradual. Every process of healing that God has placed in our bodies is still His work, for He created those processes. He also heals the wounds of the mind and heart, the scars that harsh words can leave. We do not always understand why some are healed quickly and others are healed slowly, and why in some cases like the apostle Paul, God allowed a thorn to remain even after earnest prayer. That was not because of a lack of faith or because of hidden sin, and we should never tell someone they are still unwell because they have not believed enough. The prophet Isaiah spoke of the suffering of the coming Savior, and the Gospel of Matthew applies that to both spiritual and physical healing, because Christ bore our infirmities. We can therefore come to Him with confidence that He is able and compassionate, while also trusting His wisdom for how and when He works.
So I will pray for you now. Lord Jesus, You see this hurt and You know the truth about this dear one. You know what the doctor has said and what has been spoken in anger. I ask You to bring healing according to Your mercy and power. Touch the mind and body and emotions, and heal what needs healing, whether it be instant or gradual, through Your direct touch or through the natural processes You have created. Quiet the condemning words that have been spoken and let Your words of truth and love define this life. Give peace, strength, and assurance that You are near and that You care. Surround this dear one with the love of Your family and help them to rest in Your goodness. In Your name, Jesus, amen.
Keep bringing your heart to Him honestly. He hears you, He loves you, and He is faithful.