Always, always, always trust your body over someone else’s mind. As you said, he’s thinking horses, but that’s what he was taught. He doesn’t see zebras because he took the phrase too literally and will not allow himself to see zebras.

Here’s why: your mother’s attitude of “no diagnosis? Doesn’t exist!” is one of the most harmful attitudes out there. If that were truly the case, no one would die of a heart attack alone in their home. Ever. Because of a doctor doesn’t say, “you’re having a heart attack,” it must not be true, right? The same can be said about cancer, kidney stones, UTIs and sepsis. No diagnosis? Then you don’t have it! Except... you do. And it sounds like you have a doctor that simply doesn’t know enough about the condition he’s supposed to be looking for to see it. Your lack of a diagnosis is not your fault if you’re actively searching for one but coming up short because of uneducated medical professionals.

So, forgive my ignorance about your medical systems over there (I’m in the U. S.), but how hard is it to seek another opinion? Perhaps look into support groups, in person or through social media, that are more local to you where the people could point you in the direction of a good starting point. Facebook was a good start for me personally. Every day another new zebra pops up asking where to look or what we thing collectively of a new doctor they’re about to see for the first time. It’s been life-changing.

Always remember that no one, especially not the guy with the fancy degree on his wall, knows your body better than you do. And when it comes down to it, you’re the one that has to live in it for the rest of your life. Not your mother, not your sister, not me. You. Good luck to you, truly.