Please go visit your counselor ASAP. Like today or tomorrow. And admit that you’re over your head. In your favor, you’ve been getting good grades all along, so he/she will see you haven’t been a total slacker. Then discuss some/all of these options with him/her…
Drop the chem for now, which allows you to double-down and focus on your math.
Approach your math teacher for help.
Go to math tutoring sections if they are offered during your study hall. If your family has the funds, consider a month or two at an after-school tutoring place like Kaplan. Your counselor may have recommendations for a tutor or tutoring company.
Good luck!