Hi, I'd like to help you with your question.
From what you said, it sounds like you have been through a lot with you mother, your mother's boyfriend and your father. You said you have tried to confront your mother about the abuse and she will not deal with it. And your father continues to be emotionally abusive.
What you are describing is emotional trauma which can cause the depression you are experiencing. This type of depression is sometimes described as a reactive depression. These types of depressions often are caused by feelings of anger and hurt, such as you are experiencing right now.
You mentioned that you have tried to repair the situation by talking with your mother and father about what you went through. Although it is important to acknowledge that you were abused and to express this, it oftentimes does not turn out to be a therapeutic experience. Those involved, particularly abusive people, do not respond to healing and repairing of relationships. Denial is the way they survive and that is not the kind of response you need right now. They also often continue the abuse because it is the only way they know how to relate.
If you are not already in counseling, you need to consider seeing someone who can support you and your efforts to recover. Counseling, in addition to finding support through your friends and other family, will help you find a better way to deal with your feelings. It is a good start that you have ended your relationship with your father until he can come to terms (if ever) with his role in this situation. This will prevent you from getting hurt any further and help you begin to heal.
There is an excellent resource you can get to help you get started with healing. Adult Children of Abusive Parents: A Healing Program for Those Who Have Been Physically, Sexually, or Emotionally Abused by Steven Farmer is full of information and helpful insight for people with a history of abuse.
I hope this has helped you,