Were my rights as a qualified employee with a disability ignored?

I got hired into a union factory in may. I knew I'd have trouble with a rotating swing schedule so i disclosed my bipolar as a disability and asked for no discipline for bipolar related absences. HR head said it was fine with a drs note i always provided. A few days ago im terminated because the mentioned absences were still on my record. No matter what hr wouldn't remove them even thou she said she would. I provided proof each time. She never told me it was not okay after all so i was devestated to be fired. Is there anything i can do? My union failed me.