Ihave bipolar,my doctor wants to put me on lithium,have anorexia also n want to know if it makes u gain weight?

I have been on quetiapine before and I went from 7 stone to 13 stone in two months, this made me so self concious which did not help me mentally at all. I do not want this to happen again. At the moment I am on lamotragine, quetiapine, larazapam, haliprodol, codeine phosphate, and loads more the plan is to decrease some of my drugs as they are not helping me and put me on lithium instead. I would really value peoples experiences of being on lithium, not only if it has made them gain weight but also if it has helped them. I go through extreme periods of mania and experience screaming voices in my head at night this is hellish and I need a little help to contain myself with a drug that will work. Any information, experience etc.. will be very much appreciated. Thank you in advance Harriet