I am sorry to read you have been struggling with staying focused at work. Unfortunately lack of concentration can be a symptom of depression. Treating the depression will help with concentration. Aside from medication how else are you treating the depression symptoms. Have you had a chance to get started on the program? The program is based on Cognitive Behavioural Therapy principles which is the most evidence-based treatment for depression.
I am in the same boat. I have a challenging job and this is something that I struggle with, both at home and work. It has taken me a while to adjust to the fact that I have to change how I work so I do not get overwhelmed. It will take time and you have to give yourself a break.
I have had trouble with depression before, having lost over a year and short term/long term memory in my early 20's. Did medication and got off medication in early 20's.
Symptoms of depression came back starting a couple years ago (mid/late 30's), and I got on medication again last July.
Lots of trouble concentrating to the point where it was affecting my work. I have gotten better and have exercised/taken medication and this combination seems to be working for me. I have good days and bad days. The bad days I have difficulty focusing on tasks, and even on the good days I have trouble with courage to complete difficult tasks involving others. I am in a job where I have lots of independence and I have to set out and maintain my own tasks and schedule.
I need to have more good days and the courage to accomplish difficult tasks. Depression is still affecting my work and I'm afraid that I may miss opportunities or lose my job as a consequence. I've given serious thought to taking a more structured job in less of a leadership role as an alternative, but this would be a step backwards.