Bless you! You are in quite a predicament.
You mention that you have your son on meds and I would suppose that he is seeing a psychologist (or, at least, you try to get him to talk to a psychologist). Ask for an appointment for yourself! Often a "consult with parent" is allowed for the sake of insurance and co-pay rules; plus you don't have to fill out all the paperwork as if you are a new patient.
If you can manage to see the psychologist (or child psychologist), ask these questions! Get help making a game plan for yourself.
Following the advice of some parent books, including the "Parenting Your Teen with Love and Logic", I am focusing on ignoring my son's "bad mouth" (my son enjoys seeing my angry reaction!), then on being a "broken record" saying, when you can respectfully talk with me in a reasonable tone of voice ('normal' voice), then I will listen.
The hardest part, for me and most likely for every parent, is to stop reacting with anger. I just about bite my tongue to make myself count to ten and say "when I am treated with respect then I will treat you with respect."
Keep asking questions and good luck!