Lithium is used to treat mania, so if you don't have the symptoms you shouldn't be taking it. The side effects you describe suggest so, especially because that is a large dose you are taking. Lamictal is used primarily to treat bipolar depression. It is generally not very effective for clinical depression. If you don't have BP I am surprised your doc put you on either of them. For sleep I take Seroquel, but like Lith and Lam, it has it's own specialty which is treating psychosis. It calms my brain down so I can sleep. Regular sleeping aids never worked. I could never go off of my meds and sleep - but that's because I have bipolar.
You didn't mention your diagnosis - just because you have a family history of BP doesn't necessarily mean that you have bipolar, and these strong meds are not preventative, they are used to treat symptoms that are already present.