What are possible reasons that my doctor keeps giving me ADHD meds for my anxiety?

Ask him or her. If you're not sure why your doctor is prescribing medications, you need to ask specific questions so that you're clear. Not all doctors are equally experienced in diagnosing and treating adhd, so this can cause some issues also. Since i don't know your case, it's hard for me to comment further. If your doctor won't discuss your treatment with you, you might consider seeing someone else.
Medication Question. I don't know. But, it surely may be that the medication they are recommending treats both. But, as you are learning here on health tap, it is okay to ask questions of your doctor. I know other docs have answered this and i agree with what i read. But, i would wish for you also some natural efforts to treat your symptoms such as with meditation, yoga, and exercise.