Unsigned ADA

Ive been working at this lab for 6 months, and now am worried on getting fired due to multiple er visits that had me out of work for a week. I dont have "sick time" built up and as it was an emergency, it wasnt planned...

It's a large company and HR is unavailable somehow like we dont have any human on site, just a phone number to call thats out of state?

I dont know what to do to not get fired 😭 im still battling with my health but am able to show up to work most the time now. My supervisor makes it sound like if I dont have a doctor sign papers saying im disabled im a gonner. But I cant get in to see a doctor anywhere for another 6 months, even just for these measly papers to be signed! I dont know what to do please help, I cant loose this job!!