I'm not a doctor, of course, but I've known some people with similar problems who were helped by medication, and you shouldn't be embarrassed or ashamed to explore this possibility with your doctor. If it works, it could make a real difference in your life.
But let me suggest some steps you might find helpful in any case. First, realize that God wants us to grow closer to Himself -- and one of the ways we do this is by learning from His Word, the Bible, as it is taught. Before you go to church, therefore, pray and ask God to help you concentrate. If you know the pastor's text in advance (perhaps through your church's website), read it several times before the service. Then take notes during the sermon; this will help you focus.
Remember, too, that God can reach us in other ways during church. The music, for example, can focus our minds and hearts on God and help us worship Him as we should. Listen to the prayers also -- and develop the habit of making them your own. In addition, ask God to help you find friends in your church who can encourage you in your walk with Christ.
Don't give up, but ask God to help you find ways to overcome this problem. Most of all, let the Psalmist's prayer become yours: "Teach me your way, O Lord, and I will walk in your truth" (Psalm 86:11).