Struggling with the Effects of My Parents' Trauma

I don’t know what to do. I would appreciate any help I can get. I understand my parents had a hard life and they handed me their traumas. But understanding them doesn’t stop my pain. They have caused me so much anxiety and self doubt, that it’s effected my life so much. I have been diagnosed with GAD, PTSD, and Depression. They’ll either normalize it or make me feel weak. I try to tell them how I feel and they make me feel like I’m going crazy and not remembering things correctly. I’m an adult now, but I still feel like a child that needs their approval. I don’t know how to be happy knowing I’m hurting them or disappointing them. Because of this I can’t do anything for myself, without feeling selfish. All my siblings have left or cut off contact. I feel like that puts all the responsibility on me. I don’t know how to deal with all the depression and guilt.