Is your problem that you are too slow and can't answer the questions in enough time?
or do you work every problem but end up with the wrong answer choice?
If you're getting a 14 you're likely both slow/unfamiliar with how to attack questions and make errors.
I suggest practicing basic algebra which will help you become quicker at assessing how to answer questions upon reading them so you waste almost zero time "thinking how to solve it" and can start calculating immediately.
To help you speed up, besides doing 300+ practice problems, make a few notecards on basic high yield properties to help you memorize formulas.