Many of the medications your son has been taking are quite powerful and not to be prescribed to a teenager without serious consideration. My best suggestion is that you work closely with the psychiatrist. He or she needs data from you to work effectively. Make sure that your son is taking the prescribed medication and taking it on time. Every day, keep a careful log of his medication compliance, how your son reports he is feeling, and your observations of his behavior and mood. Take that log to every medication appointment so the doctor has more to work with than your son’s and your subjective sense of how the weeks or months between appointments has gone for him.
Meanwhile, your son should also be in individual therapy to learn nonmedical ways to calm himself and to manage his life to reduce the causes and his responses to his anxiety. It’s not wise for him to think that only a pill will help him. That can lead to psychological addiction (even if he doesn’t have physiological addiction). Encourage him to work with a therapist so that he can take more charge of himself and his life.
I wish you both well.