Im so sick of this happening! what should i do?

okay i have blonde hair, blue eyes, and beige skin. my ethnicitey's include spanish, native american, irish, austrailian, welsh, german, polish, and swiss. evreytime it comes up and i say native american or spanish people laugh and me and tell me im lyeing! im not lyeing some of the people on my mom's side are native american and some are spanish. i have both those ethnicitey's in me! what should i do when people tell me im lyeing!!??