Gotta get it off my chest, I've been doing next to nothing at work for months.
Why would you do nothing while you're at work?
Because my boss is crazy and he makes me work on the same shit every day.
Sometimes work and feel monotonous, but if you feel like you're doing the same thing day after day and you're not happy, then it may be time for a change. Work doesn't always have to be fulfilling, but if you don't feel productive at work then it's bound to negatively affect your mental health. If you can't make changes at your job so that the work is more meaningful to you, then maybe it's time to look for a new job.
I'll just say it's a problem with my mental health.
You shouldn't say it's a problem with the mental health if it's not. You may just need a change of environment and a different career path potentially. I would recommend looking into alternatives for yourself.