Wheelchair without prescription?

Hi, I'm 19, chronically ill and still pretty active despite it. I've spent over a year wanting a wheelchair but never felt I needed it (imposter syndrome maybe?). Though I've recently comes to terms with the fact I do.

While over a year ago I could still walk a good distance, just had a lot of pain and my knees would buckle. I purchased a cane and rollator which I then told my doctor and he was okay with it and just insisted I used them correctly so I did.

I now can no longer walk longer than 5-10 minutes without severe debilitating pain, and often collapsing causing injury.

The problem is I currently lack a definitive diagnosis. I'm in the process of being tested for hEDS/other EDS types. I meet the criteria for hEDS though lack the diagnosis due to extremely long wait times for a geneticist. So I fear if I bring up a wheelchair to my doctor it'll be immediately shot down since I'm not diagnosed yet.

I cannot afford physical therapy so my doctor has me doing some basic stuff at home, which hasn't helped much, though I still do them ofc. It's been 5 months with these exercises, and I only continue to worsen.

I was wondering if it's okay for me to get myself the wheelchair before asking my doctor? I see him in 2 months and idk if I can wait that long to be able to leave the house again. I understand the risks of deconditioning but tbh I feel like I would be less deconditioned with the freedom of leaving the couch and getting out of the house.