Don't be discouraged!
I, like yourself, have recognized that God has given me a gift of music by ear (one, that I have, to my dismay, sat on for years).
I am in my early 40's now but my desire is strong. I have prayed and asked God to develop this gift he has given me!
I received so much encouragement from this site and the other musicians here who have encouraged me!
Meanwhile, I sing in the praise and worship at my church and I have teamed up with the music director to teach me more theory to go along with playing by ear! My desire is to play in church!
I have also contacted another "anointed" music director at another church just to sit, listen, and receive advice on how to grow in the music ministry.
Lastly, do not sow doubt or discouragement into your life by comparing yourself with others that have already progressed in their musical gift for God has a purpose and plan for each of us. Exercise faith by getting busy praying, playing, and preparing.
God knows your heart and will make a way if this is His desire for you!
I'll keep you in prayer!