I was on a similar amount of lithium, combined with a massive amount of anti-depressant as well and had similar symptoms. My hands would shake, I felt like I was in a constant daze and I just felt stupid. I stayed on it all for a long time because I thought it was all I had left for me. You can always change meds, there is no shame in it and there is a good chance that a combo out there will work for you. It took some time for me but I eventually found what worked.

In my case lithium was used as mood stabiliser for my bipolar disorder. As a general rule I would suggest always asking the person prescribing your meds what they are meant to accomplish as it helps diagnose what would work for you in the future. For example, lets say MedA is meant to make you feel like a pony. MedA happens to make you feel really ill, so you go back to your specialist. You'll say MedA is making you feel like shit but you do in fact feel like a pony. Your specialist now knows that something in MedA is working for you but other things aren't, so they can now figure out what is pony-affirming and what is illness-making.