Stubborn Coyote

Hello, I am new here. I am 25 years old and I recently went through cardiology testing to determine why I am having spells of tachycardia and dizziness upon standing up. I'm wondering if I am seeing the wrong doctors. My GP and Internist ordered blood work and it all came back squeaky clean, so I was referred to a Cardiologist team. They did an ECG and tested my blood pressure, and revealed that my blood pressure was dipping slightly, which they said indicated a problem and ordered a tilt table test, echocardiogram, stress test, and 30 day event monitor. I thought we were definitely getting somewhere! Echo and stress test showed my heart is healthy and functioning well. TTT was complicated. I was fine the first few minutes on the table, but nausea hit me out of nowhere and it quickly felt like my whole body was on fire. My blood pressure had dropped. I then had a panic attack (I have agoraphobia and panic disorder) and my blood pressure went back up. They gave me nitroglycerin, which caused pooling and pain in my arms and legs. I was very weak and woozy but didn't faint. They were only testing for syncope, so test was negative. My event monitor apparently showed that every time I recorded, my heart rate increased considerably. All events were recorded after getting out of bed, picking things up, bending over and standing back up. During my last appointment, I saw a doctor I had never seen before, and she insisted I take a beta blocker, but couldn't provide a diagnosis or even a discussion about my test results. She said I am just dehydrated and didn't believe me when I said I drink at least 80oz a day and am allergic to caffeine, so never drink coffee or tea. She said I *may* have Inappropriate Sinus Tachycardia. She didn't sound confident and I don't believe it, as my heart rate returns to normal if I sit or lay down. I experience fatigue, dizziness, gray-outs, tachycardia, a HR increase of 20-50bpm when I stand, and sometimes there are days my heart rate doesn't drop below 120, reaching the 150s with minimal exertion. I also have many other issues I am reading may be associated with dysautonomia, such as decreased sweating abilities (I don't sweat despite living in Florida), unexplained itching and hives, exaggerated allergic responses, headaches, asthma, brain fog, exercise intolerance, irritable bowel, and severe anxiety and panic attacks. I feel like my doctors are acknowledging that I have a problem, but don't know what to do with me. I feel like they have put me on the back burner because my cardiologist has not even seen my event monitor results yet, but had a team member throw me a tentative diagnosis anyway to get me on meds. I refused any prescription until I get to the bottom of it, so now I'm waiting for them to release my test results so I can get a second opinion. My problem is, I am not sure where to go next. Has anyone had a similar experience and know what my next move should be? Thank you!