Your result
Australia — Citizenship by Descent
Possible
You were born in Australia on or after 20 August 1986, the date birthright citizenship narrowed. Being born there is no longer enough on its own, so whether you are already an Australian citizen turns on facts we do not have yet. Note that what is in question is citizenship by birth, not by descent: descent applies only to people born outside Australia, so it is not your route either way.
You are an Australian citizen from birth if either parent was an Australian citizen or an Australian permanent resident on the day you were born. Permanent residence is enough here, which catches a lot of people whose parents migrated and never naturalised. If neither parent qualified, there is a second route that depends only on you: a person born in Australia who then lives there for the first ten years of their life becomes an Australian citizen on their tenth birthday, whatever their parents' status was.
Either way the next step is the same. Apply to the Department of Home Affairs for evidence of Australian citizenship. If it confirms you are a citizen, you can apply for a passport on the strength of it.