Depressed

My side of the family is falling apart. I feel like it is my fault because I am trying to set boundaries. My mother was verbally and emotionally abusive to me and my siblings for 15 years and with a baby on the way I need to stop letting her control and manipulate me. My 14 year old brother is in a residential treatment center for mental health issues. Because I said I wasn't coming to Thanksgiving my mom is not holding it anymore and my brother won't get a Thanksgiving while he is home. I feel responsible for him and have felt guilty and depressed for 2 weeks. I feel so alone and Eyore ish. I don't want these stess and depression hormones in my blood to get to my baby but I don't know what to do. I feel awful. I see a counselor once a month and she has helped me with the boundaries, but not the depression. Does anyone have any advice?