You are experiencing what a lot of us go through and no doubt will again. You know you can do it but it is at the course where your problem is. Change your mental approach. Go to the course as if you were going to the practice range. Forget scores, concentrate on hitting the ball as if you wer at the range. It is tension and negative thinking that puts us in this position. Go and enjoy, not endure. Eventually when your confidence builds the scores will come themselves