You don't have to see the medications as a permanent thing from the outset. You may have to take the meds to give yourself the focus/ability to start changing your other habits. After that point, you might be able to build up enough momentum that you'll be able to work on yourself in other ways and eventually not need the meds anymore. But depressed people often need that initial boost to help move them out of the cycle.

Also, not to argue against "depression" or meds or anything, but... sometimes, especially for people in the first decade of their working career, we might be trying to convince ourselves we "should" be enjoying our career circumstances even if we just don't. Those shoulds can certainly exacerbate depression. I'm just saying that your underperformance might also be an indication that you don't like your job, which is totally ok.

Finally, one of the simplest harmless things you can do to start, that you might be able to motivate yourself for, is drink a lot more water, and take a B vitamin every day.

But yeah, main thrust - take the meds, trusting that you may find it easier to motivate yourself to take other healthy steps in the future.