Will a course help ME?

hello I am looking for some advice regarding gmat prep courses. Will they help me more than self study. I have been doing self study with the manhattan gmat strategy guides for the past six months but have failed to significantly improve my score. In many ways I feel that too much time elapsed and I forgot things I learned when I first started. Do you think that I should take a course? FYI, my first score was a 540 and my best is a 590. My most recent score was a 560. These are all practice test scores. I take the real thing this Saturday. I would like a 650 to get in to my school of choice.

Thanks for any advice.