I don't fit any bra cup size

Okay so recently I realised why I was never comfortable with any bras that I got. Of course the  size around my body is easy I'm a size 10 (Aus sizes). I do not have normal big sized boobs for a 19 year old, I'm somewhere in between a 10B and 10C, both is either too small or too big. Is it "normal" or possible that I can't fit a bra size from the shops? Or can you get special made ones to fit you 😕