Since OP is of the age to be concerned about completing FAFSA, and my understanding is that an A2 visa has a maximum limit of five years with no renewal available, it’s possible that at the time of OP’s birth the parents (or at least the mother) were in the United States in a non-diplomatic capacity.
I don’t know the answer to the FAFSA question. OP’s situation is unique enough that direct contact with a federal government FAFSA specialist is probably warranted.