Trying to get a diagnosis

Hi there, I’m currently trying to understand all of my symptoms that I have suddenly been experiencing. I have all of the symptoms that comes up under Multiple Schlerosis and have had to drop out of university because of it. I have had 2 brain MRIs and one spine MRI and all have come back as negative of any lesions however both brain exams show sinusitis and mastoiditis (both of which I have no symptoms of). I have also had two neurological tests which both also came back as normal. Everyone keeps telling me ‘it’s all in my head’ and that I have bad anxiety but I keep trying to explain to everyone that I didn’t have anxiety before my symptoms came and the anxiety is a result of my symptoms. Is it extremely rare to have MRIs with no lesions in brain or spine if you have MS? I’m only 19 so I feel that doctors aren’t taking me seriously. Does anyone have any recommendations of how to be heard by doctors and taken seriously?