Where to start? "adult unadoption"

As long as the adoption was done legally, there is no way to be un-adopted, or to void the adoption. However, your birth father or another adult male could adopt you. Adult adoption is legal in all states, I believe. You don't need anyone's permission to do it, either. That would put a different name on your newly-issued birth certificate, and give a different person those "legal rights" that you don't want your ex-stepfather to have. Alternatively, you can do a legal name change yourself now, and you don't need anyone's permission for it. And a will and a living will should take care of anything another related adult might try to do against your choices. But neither of those are foolproof, which is probably why so many adult adoptees choose to have someone else adopt them rather than following those processes. Good luck.

Thank you very much! I guess I will just start looking for name change info. I don't want to ask my dad to re-adopt me as I know it would cost. But at least I know where to go now. It seems a bit silly that I can't undo what's been done, since I'm an adult and the ex-step father may as well not even exist now. Thanks! :D

I agree. I think that it is completely rediculous that as an adult, I can't have say on whether or not I want to be a part of my adoptive family. I, personally don't want to be part of my afamily anymore. And everywhere I look, people are saying that my birthfather can adopt me. Why in the world would I want to be adopted for a 3rd time?? And why would I want my birthfather to adopted me??? I want to legally be his daughter again, so I should have every right to be un-adopted!! I was un-adopted when I was younger because the family didn't want me in their family. So why can't I do it now????

Adult adoption in my state and my neighboring state is not expensive. Research your state and good luck!