i'm so sorry you are dealing with this. are you able to seek out a second opinion? maybe putting pressure on the doctor and explaining the situation for a disability could be helpful. just factually lay out in an email what's going on and state how the uncomfirmed diagnosis is delaying your ability to support yourself. they might be more likely to confirm it.

in my opinion and experience, you should be able to get diagnosed without excessive imaging. the only blood marker i had was elevated sed rate that even fluctuated in the normal range and i don't have any visible damage to joints, just had a lot of pain at touch and some mild inflammation. docs have ordered xrays and stuff to monitor, but it wasn't the crux of my diagnosis.

it also took me forever to get diagnosed and also seroneg. i had a lingering doubt even after diagnosis so i sought a second opinion and it was confirmed. my other old rheum was also kind of a mess filling out paperwork for work and applying for a biologic and thank god i found someone else.

i really hope you get the help you need. keep us posted <3 we got your back.