firstly, the most important thing is to make an appointment to talk to your teacher as soon as possible and explain your concerns. they can offer you better advice than any of us can as they will have a far better idea of your potential.
if you decide to stay in advanced and are still concerned over your ranking, than perhaps you should consider asking your teacher to recommend a good tutor? Tutoring can help refine your style, understanding and technique, thus improving your ranking.
lastly, don't rush your decision. you will need to decide reasonably soon, but make sure whatever decision you make is definately the one you feel most comfortable with as it will be difficult to change again later on.