The things we do to fit in, things we do to be considered “normal”. In your situation in my youth I would do the same.
I had someone ask me if I was a “mischling” mixed race because my constant answer to the question “where are you really from” was the UK and my parents are British Citizens. The person was so desperate to have a reason for why I’m Black but claim to be from the UK.
To anyone reading this and asking the 100% question, research your own ancestry and genetics and determine if you are 100% anything before challenging someone else’s ethnicity and ancestry.
And to the person in this reply thread who said he doesn’t believe you, my response to him is “how dare you!”. His comment is grossly insensitive and should be kept to himself.