Dizziness and Nausea - Seeking Advice

I agree with WooZoo here, unfortunately those symptoms are found in a lot of things. Have you had your iron levels checked? It could be iron deficiency anemia. I would stress to your doctor that the symptoms are unusual and interfere with your life. Push further and ask what they think it could be other than your height (which tbh I've never heard and sounds kind of strange for an explanation). You have to be your own advocate - if something doesn't feel right then keep looking and asking until you find an answer!