I need to journal at office as therapy but my …

I have OCD and Depression and I have been told by my psychotherapist to write down my thoughts and issues in a small notebook soon after they happen. This helps me process my symptoms and manage them better in daily life. Basically it keeps me sane. The writings are obviously by their very nature, deeply personal and private. The writing takes only 10 minutes cumulatively throughout a day, 1-2 minutes each time.I work at customer service and They have set up a rule where I can’t use the phone or use the diary. Even though other co-workers are okay to do so. They also throw down much of the work on me since I am so passive.Now the thing is that lately I have not been able to bring in as much sales that my Manager (lack of social skills) requires for his promotion and he has stepped up the gear. On the past two days he has rebuked me in front of everyone several times for using the phone and writing. However it was only 10 minutes on mobile on free time trying to find Assertive techniques for the workplace. He says that he has zoomed in and seen everything I did and the websites I went through on my mobile (he said I was on chrome and even more) and what I wrote in the diary.Now there is those half-spherical black cameras right above my desk in the ceiling. All the cameras in the office are recorded 24/7 and the records stay there for 4 years. It also seems that the cameras are very zoomable down to seeing what you do on your phone and writings.I need a way to write my journal privately without the cameras seeing. I am not allowed to go out of my desk and everything is camera covered. I also don’t want to use my phone since using it is forbidden to use the phone other than for office work. Then there’s the chance of Android getting hacked.Any suggestions on how I can write in my journal privately? Can anyone suggest a technique or a setup, process or DIY gadget?​PS: This is Asia and revealing your mental illness is not an option. It leads to throwing you out of work, social outcasting etc. I do have said that I can’t handle stress or I will have trouble with this work or that and they have laughed, insulted and stepped up the pressure even more to “toughen me out”. So talking about it is not an option. Also, jobs are extremely difficult to come by, so I can’t leave this.