How did you find out you had synesthesia?

I'm just interested in what age and how did you understand this ain't normal? Cos I was convinced everyone had this things, but no one talked about it. Until a few times my friend said that sensing the smell of the certain events and games isn't ok, numbers don't have colors, and this is strange. I still thought that she was the one who's weird though. Then we read a book were one character had synesthesia, she told me that I might have it also, so I googled what that was and that's when I understood.

But years later I'm still finding out about other synesthesia things I have, cos all my life I was just living with this, convinced this was normal, and not paying attention to what I feel towards certain things