I know the feeling of drowning...
The only thing I can tell you is to take whatever it is that makes you happy (I don't mean life-saving happy...for example mine is taking a bath) and hang onto that. Don't forget to do whatever it is. For most of us, and as you know, sometimes the most you can hope for is to stay at the level you're at. When I was at my worst, I was reading about what others do and one woman played mind-numbing games online. I started to do the same. When I was "healthy" I would have looked down on such behavior and judged, but now I know what depression is like and, so..... whatever it takes to get you through the day, I say go for it.
I have been on a few meds and most needed supplemental medication, but the main one that I always have gone back to is Wellbutrin. Now I take that with a Zoloft chaser. Perhaps it's time for you to try something new.
I'm sure that you are aware of the benefits of sunshine and some form of exercise....
Just my 2 cents.