Thank you for your letter -- and I'm sure many people will pause to pray for you as they read it. The Bible tells us to "pray for each other so that you may be healed" (James 5:16).
I'm thankful you've been in contact with a doctor who has been able to diagnose your problem. But have you continued seeing him, and are you following his instructions concerning treatment for your problem? I'm not a psychiatrist or psychologist, of course, but I know that problems like this often are caused by chemical imbalances in the brain, and medicines can often help overcome these.
Don't let your emotions guide you about this; when you're feeling good, you may be tempted to think you don't need to take any medicine -- and when you feel depressed, you don't want to take it. But God often uses medicines to heal us, and we shouldn't turn our backs on them. One of the Apostle Paul's closest companions on his missionary journeys was Luke -- a medical doctor (see Colossians 4:14).
Most of all, I urge you to put your life into God's hands by giving your life to Jesus Christ. He knows what you're going through, and His love for you will never grow weak or fade. In addition, let the Bible's promises encourage you every day -- no matter how you feel. The Bible says, "The Lord is a refuge for the oppressed, a stronghold in times of trouble" (Psalm 9:9).