Well, if nothing helps there’s nothing you can do. The thing is that the only way to know that is if you tried everything, and that’s impossible, even if you had 3 lifetimes.
Maybe you’ve been to 3 different therapists, 2 psychiatrists, tried 4 kinds of psychotropic medications, 2 different diets, numerous exercise routines, and engaged in more outside activities and social groups then you care to remember. Well, maybe those therapists and psychiatrists weren’t the right fit, you haven’t found the right medication, exercise or diet, social group or activity. You can always try something else, a different combination, a new activity, a different social group.
I’m not suggesting you focus on the external, as I tend to believe it’s more about the internal factors than anything else, but all these things are pieces of the puzzle. They all factor in.
What’s not a good option is not doing anything and resigning yourself to being depressed. That will definitely leave you exactly where you are, which doesn’t sound like a good place to be.