Let’s separate the issues. You’re in advanced classes for your age and struggling. The semester has still a while to go. Math is foundational so you want to learn it b4 moving up.
Not sure what you define as selective but there are colleges where kids got Cs and others where 4.0 and perfect test get turned down.
When you are ready to build a list, you will include those that meet your desire including budget, size, location and more.
Selectivity doesn’t = success. Some of the top perceived universities in the country admit half or more. The school with amongst the most National Merit Scholars is a southern public with a high acceptance rate. And the school with the highest percentage of all students being National Merit ( over 25% at last count) accepts more than 60%.
Top students abound at likely every flagship and tons of privates. And in the end, you will make your success, not if you go to Wesleyan or Wyoming.
But focus on learning. The college list is irrelevant to your grade. And the grade is less concerning than you lose the material as you might continue forward.
I assure you entry into many fantastic colleges is, without knowing your overall profile including ECs, etc - , but it’s likely very assured.
Do your best to lift the grade and more importantly learn. College selection will take care of itself.