Do I have abandonment trauma?

This is a good question that you ask.  I see that you mentioned abandonment as it relates to your step dad who walked out of your life.  Generally speaking, abandonment can be a cause of trauma in one's life.  Abandonment trauma would be the behavior and emotional response that one has as a result of the abandonment that they experienced.  It would be important to know how the abandonment has affected your life as it relates to emotional health, social life, and even physical health.  Some questions to ask yourself is:

1)  What emotions or feelings come up as you think about your step dad walking out on you?

2)  How has your step dad walking out on you impacted your life?

3)  What has caused you to distance yourself from everyone?

In general, the effects of trauma can include avoiding situations and conversations that remind one of the trauma, difficulty sleeping, difficulty concentrating, anxieties, and suppressing the emotions.  It can affect someone's ability to focus at work, school, or personal life.   

I am also sorry to hear about your best friend passing away last year.  It sounds like you are grieving that.  It is okay to allow yourself to grief meaning that it is okay to feel angry, sad, or hurt by the loss.  Perhaps distancing yourself from everyone is part of that grief.  

I also would like for you to know that healing from abandonment trauma is possible regardless of the trauma that one experienced.  It is about overcoming the abandonment trauma instead of just pretending or forgetting that it existed.  There are healthy coping activities to engage in to help overcome trauma such as relaxation, mindfulness, journaling, or engaging in favorite hobbies.  Abandonment trauma can also trigger negative, unhealthy thoughts such as "I am not good enough" or "people tend to reject me." 

Therapy can be beneficial in helping one explore and engage in healthy coping activities to overcome trauma.  It can also be beneficial in challenging the negative thoughts that was brought about from trauma.  An encouragement to those that have experienced trauma is to see themselves as a survivor and not a victim of trauma.