1. Go to a LabCorp or whatever independent testing lab in your area. Find out if they can do the test you want, how much it cost, and what they have to have to do it.
2. Call your insurance company let them know what is happening and that you are feeling unheard and attacked by your doctor and that this one test would allow you to feel comfortable with the diagnosis your doctor has stated. Potentially your goal is to get them to approve this one test.
3. Go to another Doctor for a second opinion. You can call your insurance yourself to get a second opinion approval. If they approve it you can at least get another opinion. I always try to get my second opinion in a different place. Like maybe the next town over so the 2 doctors are probably not affiliated.
It may not work out for you but you will have more information and maybe even the reason your doctor refused this test.
These are just ideas but they may give you some next steps.
Advocate for yourself because no one else will.

I went for a second opinion once, I told him I felt medically raped by the first doctor because when I said anything to him I got the feeling he thought I was insane. By the way I wasn’t. I was right. I’m 68 now but I was in my early twenties then and they just thought they could placate me.
Harley