Workplace stress can be caused by factors like unreasonable hours or workloads, workplace restructuring, and a lack of health and safety precautions against hazards. But you must raise it with your employer so they have to opportunity to manage it.
Options available to manage your stress could be offering sick leave, providing support like counselling, changing your duties, reducing hours (with your agreement), or moving you to an alternative role (again with your agreement).
If you’ve raised the issue with your employer and they haven’t done anything about it, you can seek advice from your union or Worksafe.
Note: If you’re experiencing stress outside of the workplace, for example, a relationship breakdown, your employer isn’t responsible for managing that stress, but they may have assistance available to you such as the Employee Assistance Programme.