It does not matter that you reported your absences or had a good reason: if you were absent from work without using paid time off (e.g. sick leave) for it, this was an unauthorized absence and, subject to any discipinary process or procedures in your union contract (the employer must follow the terms of a union agreement), you can be terminated (or if the employer chose instead, and the union agreement permits, demoted, suspended, pay cut, etc.) for it. There is no legal right to take time off to care for your mother, so if you did not use paid time off, you can be sanctioned for this.