B in math... advice?

Make the effort to move the grade to an A. You are apparently treating a B as an anvil around your neck. Put that aside.

There is precious little students can do to azure they have produced an application that assures admission to the Ivies and that includes students with fabulous credentials. Your grades are not perfect and you have not taken admissions test yet.

You are on the road to becoming an excellent college applicant. Explore other options.