Hi, I'd like to help you with your question.
I agree with you, it does sounds like you are depressed. Major depression is characterized by not only depression, but suicidal feelings/attempts. The only way to know for sure is to be evaluated by a therapist or psychiatrist, but your description of your symptoms do sound like depression.
You most likely feel depressed because of your childhood. You were physically, emotionally and sexually abused and neglected. There was no opportunity for you to connect to anyone and get the love and attention you needed. You had to fend for yourself and try to meet your own needs. When you go through childhood without getting your needs met, you lack the feeling of security and belonging that all children deserve. Children who are abused have a hard time understanding why they feel as they do and what the cause of their feelings are. Because of this, they often turn the feelings onto themselves, convincing themselves that it is their fault for being unlovable. This sometimes leads to cutting and almost always leads to depression.
Cutting yourself is a sign of deep pain. At the time you had no where to put your pain. You tried to tell your mother what was happening with your step father and she just turned it back on you, blaming you instead. This caused you deep pain, along with all the abuse you suffered already and no way to release or express how you felt. Cutting provided some temporary relief, but since it cannot solve your problems, you never feel your pain is resolved.
Getting help for yourself and getting better may involve medications, but medications are only needed if you feel you cannot function in your life. Therapy and self help are the best ways for you to address your past and help you recover from the abuse and trauma you suffered. You mentioned that you did see a therapist for couples counseling, but individual therapy would be the best option for your situation now. Between the support from your family and the help of a therapist, you can recover and feel better. It may not feel that way now, but you can. Here are some resources to help you get started:
To find a therapist, ask your doctor for a referral. Or you can search on line at http://therapists.psychologytoday.com/rms/.
You can also join support groups either on line or in person. Here is a link to help:
I hope this has helped you,