Rumination and unhelpful coping strategies. TW: Addictive tendencies

I struggle with rumination as part of Bipolar, OCD, CPTSD. I am also ND and have ADHD and ASD. I have been struggling to function and my productivity has been declining, and I'm often finding myself stuck in rumination for several hours each day. I usually struggle with focus and motivation on a good day, but I think the stress is adding to it. Not being able to do things is also creating stress. I feel like my ADHD is feeding into my mental illness and vice versa. I am finding myself wanting to turn to things that will make things harder in the long term. I know developing addictive behaviours may give me relief in the short run, it'll calm my brain, help me think clearer and make it easier to concentrate on tasks. I am also aware this will create health problems in the long run. I need something to calm my brain and help me function without having negative consequences. I find once I am able to do things, my mental illness symptoms get better. Does anyone have healthy ways to cope with rumination, mental illness and ND? I'm currently on bipolar meds (my pdoc doesn't want me on ADHD meds) which helps me stabilise my mood to a certain degree and I'm trying to work on myself in therapy, but I am still struggling a lot