Your Dad has no legal right to intervene in any way in your affairs unless he's been appointed your legal guardian in some legal manner. You're an adult. Now, I don't know if you have a history with drug use or criminal behavior or mental confinement that led to his being your legal guardian, but strictly as a parent, any contact he has with your doctors is an invasion of your privacy. Simply tell your doctors they don't have your permission to speak with your father, and that ends that. The person above is right, though, that the law can't stop him from saying nasty things about you -- only you can do that by moving out and not speaking to him until he gets over this. He may in fact feel some guilt for what you're suffering, and expressing it in anger toward you. I went through this with my Dad, who had a real hard time with having a daughter and a son who both developed severe anxiety problems. What you don't mention is if you're in talk therapy -- you should be, and that might be a place where you and your Dad can work this out, if he's willing.
If you are 32 and presumably living with your dad, legal action is not necessary if you can be on your own. You can leave without needing any kind of legal intervention, if you can support yourself. Are you on any disability? Can you cover the cost of a place to stay and food? There is no legal intervention that can keep your dad from saying snide things.
It is more than just aspertame. Do you know what sucralose is?....do you know what MSG is? Try some research and don't ever give up!