It is good to talk with your high school counselor in order to think through when you should sit for the test. The math level that you are taking in your junior year will be something to consider when making this decision. You will also want to leave the option open to retake the test, as many students improve their scores on the second sitting. This article talks further about retaking the SAT.
If the SAT or ACT seem like a challenge for you, it is good to know that more and more colleges are becoming test optional. Each year I work with students who do not take the SAT or ACT at all, and they are still able to attend colleges that are a fit for them. But before making that decision, you will want to make a list of colleges that interest you in order to know if this strategy can work for you. Here is a list of colleges that are currently test optional. You should research each that is of interest to ensure you understand any unique attributes of their test optional policy.