I'm concerned that you refer to your ex as your drug. No healthy person wants to be depersonalized as you describe. What were you bringing to the table in the relationship if she was your "drug?"
People are not drugs to be exploited for one's self-medication, particularly in excess and to the extent that it is toxic for both parties. They instead have feelings, thoughts, and free will to consent to love relationships. Relationships require give and take. They should not be used as substitutes for seeking professional help for mental illness and doing the hard but worthwhile work that is involved in therapy. I suspect you may have been using her as a substitute for seeking professional help for your depression. That's not fair to her, nor is it good for you.
Since she has left you, I recommend that you let your ex and her memory go and learn from the situation. Work on addressing your depression and any other issues you are struggling with by seeking help from a professional counselor or therapist. There is absolutely no shame in that. Before you attempt to be in a love relationship, you need first to be healthy yourself. Go forward and seek to be as healthy as you dare!