To increase your Quant score, you can do two main things: strengthen your skills in weaker topics and reduce the number of careless errors you make.
To strengthen your skills in weaker topics, consider which topics you have trouble with and would rather not see on the test and, for each one, review the relevant concepts and strategies and practice until you feel confident in the topic. Even though you're at the stage of taking practice tests, you should still do some of your practicing untimed to give yourself time to learn to get the questions correct.
To reduce the number of careless errors you make, you can seek to execute more carefully, doing things such as making sure you answer the question asked. Also, you can look for patterns to your errors, possibly by keeping an
error log. In many cases, just a few patterns of behavior cause most of a test-taker's errors. So, it may be that, by identifying and addressing a few patterns, you can increase your Quant score significantly.
Also, you could practice one Quant topic at a time using the streaks method, which is discussed in the following post.
How to Ace the GMAT Using the Streaks MethodThe streaks method can be brutal, but it can also be very effective.