Why is my mom being so mean?

My mom keeps calling me a disappointment because I forgot to do my wash and clean my room. She tells me I never do anything even though I do so much for her. One time she even called me a disgrace after I took two pretzels to eat after she told me only to take one. What can I say, I was hungry. I just don’t understand what I do that is so wrong to deserve such names? Also, we’re not poor or anything too so the pretzel thing kind of came off as weird to me.