Struggling to Get a Diagnosis: How to Make Doctors Listen

I told my Primary Care my concerns, of blacking out when standing up, and he told me it was anxiety. I then slightly fibbed and I had chest pain(even though I knew my chest pain was from asthma). He said my EKG looked normal, and had to practically beg him for a referral to a cardiologist. ( I do not see this Primary care anymore) Thankfully my cardiologist already knew what POTS was and suggested we do a tilt table test for it. I got my diagnosis from that.

I showed the doctor what happened if I stood. She saw my heart rate jump to 160 very quickly and so she had me sit. It scared her, to the point she told me to go to the ER if I was at 170+. She referred me to the cardiologist and they saw the same thing so I got my diagnosis