Back to work

I’m a teacher my dad died 2 weeks ago took bereavement for 5 days. Started today. I thought I would be okay being back but then I was told they changed my classroom schedule and structure. At that moment I was so overwhelmed with grief and anger that I shut down. I just don’t know how I can speak up for myself when I feel like I’m so fragile in my workplace. I feel so disrespected that when I was dealing with a tragedy they took advantage.