Hi,

You definitely need some more practice material. If you're weak in Quantitative Section, you may also need someone to help you brush up all the concepts so that it becomes easier for you to solve the practice problems.

A few pointers while you practice Math:
(i) Read the language of the problem very carefully. Most mistakes happen here.
(ii) Atleast for the next one month, spend time on problems. Even if you get a right answer, try to find alternate ways of doing it. Try to change or twist the problem and solve it again. That is the best way to learn.

Whether you can get a 550+ depends on two things:
(i) Your current level in the two sections
(ii) How you plan your preparation and implement it