Do you think my mom cheated on my dad?

I am half white, half black. except I do not look black. my mother, I think she may have cheated on my father but I am 16 and I always bring it up (and when they get mad I say I am merely joking) anyways, yeah, I look full white. long thick dark brown hair, fair complexion, freckles, blue eyes, thin nose. (unlike that of my father's lmao he has a huge nose). Do you think my mom cheated on my dad? or could it be possible that I am half black? My sisters say that like african american women I do have a high butt? like where it is placed on my body... I'm thin like my mother used to be but I have a big butt ! that is probably the only black in me lol.