Job Threatening Me Over Sick Days

Location: Rhode Island, USA.

I’ve been working at a large retail chain for almost a year, and I am a part-time/hourly assistant manager. Today I called out because I am experiencing a severe migraine.

My manager responded with the following: “there is no coverage you will need to work your shift. Your attendance history is not where it needs to be at all. This is going to be disciplined. (Redacted) and I are already working. Im working in another store with (redacted) right now. You will need documentation for this call out from a Dr if you do not come in for your shift tonight. I cannot find coverage. Im sorry.”

I understand that my absences have been a concern, however my callouts haven’t been all for the same issue. One of them(7 months ago) was due to an injury I abstained at work, and my previous boss never reported my injury to workers comp (like he said he would). Instead he filed for FMLA which took 5 weeks to find out I wouldn’t be covered under (length of employment). After that he applied all my built -up sick time without asking me, and then told me I would be fired if I didn’t come back tomorrow. Accommodations “don’t exist” at my job. HR could not undo my sick time so that I could instead apply for compensation through the state. Due to the way this was handled, I believe it looks like I have about 5 weeks of unexcused absences. My doctors notes were never uploaded or submitted anywhere. Needless to say this boss was fired for not following protocol at the job(many reasons), but my case never got fixed. So I’ve been “on thin ice” for something that is entirely not my fault.

Then, 2 months ago I called out for another migraine. I have had no other callouts, but I have swapped shifts with other managers when we needed a day off for something.

My concern is that my manager seems to be implying that because there is no one available to cover my shift, I am expected to come to work regardless of my medical condition. I also feel uncomfortable with my current illness being immediately tied to my attendance history.

I have a few questions:
1. Can an employer require me to come to work when I am medically unable to perform my job simply because they cannot find coverage?

1. Can they require a doctor’s note for a single sick day, particularly if obtaining that note would require me to travel while experiencing a severe migraine?

3.If they discipline or terminate me over this absence, would there be any legal protections available for health-related absences? (Would I still be eligible for unemployment?)

1. Should I be communicating directly with HR at this point or requesting any type of formal accommodation?

This job isn’t my forever job, but for now it is all that’s available to me in my area. I’d like to know what my rights are, and what I should do in this moment to protect my butt in the event I get fired/punished for this.