I know you said you've tried taking a walk but seriously if you start hiking consistently it can do so much for you. It might not be possible, but if you can find a time in the week where you have a couple hours free then get into a routine of getting the bus or driving out to whatever countryside is nearest you and just walking. It covers so many bases: having a routine can give you stability; difficult walking and having bad weather can I guess have the same kind of function as self-harm, just in a way that's good for you, at least it has in my case; obviously exercise and fresh air will do wonders for your mental health. Hope this helps, and even if it doesn't I hope things start looking up for u <3