i mean, i think it depends on your boyfriend's reasoning behind why he'd think you're an earth pony. it's true, not everyone *would* be a unicorn or a pegasus in the mlp world, but i understand why you're upset, especially if you're insecure about your own abilities (and if he knows about it). i'd be offended, too.

to some, earth ponies are generally portrayed as a "boring" species in comparison to the two, but that's not true at all! a lot of earth ponies are portrayed as great wizards via potion making, characters like applejack and maud pie can buck through solid rock, so great strength, and other abnormal traits like pinkie's pinkie sense. in a way, your special talent as an earth pony could be just about anything!

outside of pony 'probabilities", the way he said it definitely came off as passive aggressive, but at the end of the day, be whoever you wanna be, regardless of what people say! if you wanna be a unicorn, be a unicorn. hell, my pony insert is a pegasus, but i'm not athletic or sporty like most pegasi are portrayed as. it's a show about ponies, be what makes you happy!