I started out in the same boat as you, scoring only 6's initially. Even though this is against what many people told me, after practicing and practicing with no results, I changed my gameplan. I decided to go slower and be more careful in my reading/answering. Even though I often had one passage left over my score went up a few points (you are bound to guess 1-2 right answers on the passage you don't finish, just make sure it isn't a passage with a lot of questions). This strategy worked for me after I decided I would shoot for a 10, instead of trying to get them all correct. I would give this approach a shot if you continually have problems increasing your score. Hope this helps.
Oh, and so you know... don't be discouraged by this right now. Keep practicing and trying different methods until one works. I was in your situation this time last year and now I'm going to med school next year, just try and keep the faith. Good luck!!