Legal Question in Discrimination Law in Illinois

Very possibly and, if they offered you no reasonable accommodation for your medical condition, this could also be a violation of the Americans with Disabilities Act if the condition is medically provable, they knew about it and this was their only "response". Unless it would be infeasible for them to provide any accommodation and is such an essential job function. You should see an attorney (employment, workman's comp, civil rights) as soon as possible to preserve your legal rights as soon as possible.