So sorry to hear life has been taking a nose dive

Some of what you've described resonates with me, and coincidentally it was happening to me while I was on lithium.

The lethargy, concentration and memory issues... It actually kept me quite depressed and apathetic to be honest, then add the host of other intolerable side effects, and it was just a miserable existence for me.

It was so bad I flushed my meds and stayed without for three years.

Lucky for me it was the only change in my meds so I was able to identify it as the culprit.

Now idk if its what is causing your current struggles, but I do strongly suggest looking into a med overhaul, it may just be what you need to get back on track at work, and personally too.

I used to supplement my diet with a monthly B12 shot, a herbal tonic for concentration (my friend gives it to her son for his ADHD) and sometimes an energy drink or two.

With all that being said, I'm now doing monotherapy and am only on Depakote 400mg twice a day and am responding well.

I think for me less is more though, trying to medicate every symptom was overkill, so now I just take a mood stabilizer and deal with the rest as they come.

I know that's not a solution for everyone, but just sharing my personal experience.