You already know that killing yourself isn’t the answer. Getting out of your parents’ complicated relationship is. I think you are getting fall out from fights they are having with each other. Instead of dealing with whatever it is that is going wrong between them, they take their upset with each other’s decisions out on you.
You are now graduating from high school. Start figuring out how to make a life on your own. Get a job or figure out how to go to college — or both. In the meantime, resist your mother’s invitations to fight. It’s pointless to argue since the fights don’t really have anything to do with you. Just tell her you are sorry that she feels the way she does (no sarcasm, please) and leave the room as gracefully as you can.
I am very concerned about your physical symptoms. You do need to see a doctor to make sure that your symptoms aren’t a signal that you are ill. If your doctor doesn’t find a cause, then see a therapist, please. It could be that your anxiety about the home situation is showing up in your body. A therapist can also give you the support you need to stay out of fights and to plan a future.
I wish you well.