I have been on lithium for over a year now. I take 900 mg of Eskilith (a common brand name). I was also on Klonipin for quite awhile as well. I'm not familiar with Risperdal-is it a mood stabilizer, anti-depressant?
Anyway, about Lithium-yes, you will always be thirsty. Lithium replaces sodium in your system and can basically dry you out. It is very important to drink as much water as you can. I know a lot of people don't like water, but there are plenty of flavored, non-sugared waters that are very good or you can try to drink Gatorade, but watch out, it has a lot of sodium.
Have you had blood tests? I hope so, lithium can greatly affect liver and kidney functions if you're not careful, so if you haven't had tests yet, I would ask about it.
The shakiness and sickness to your stomach could be the combo with your Risperdal-I'm not sure, but you should really ask your doctor about that.
I used to take two Klonipin at night to help me sleep. I believe they are a bit milder and not as addictive as Vallium is, but I'm not sure. You may not be taking enough mg at one time to be effective, especially if your Lithium levels aren't right. Eventually I moved on to Serequel an anti-psychotic often given to those with Bipolar to help them sleep and quiet racing thoughts and hypo-manic tendencies.
I'm not an expert in anyway. I just know from experience. Getting on the right meds in the beginning can be very hard. Remember to be open and honest with both your psychiatrist and your family doctor-even if you're not sure of a symptom, mention something anyway-this can be very important!
Hope this helps!