Soft drinks are total acid that your body has to deal with. Distilled water with a little lemon at room temperature is probably just what you need. I like spring water, but I read that the distilled water is better for detoxing. Your liver and gallbladder are located in the region you mentioned you were having pain. My favorite forums, Liver Cleanse and Ask Andreas (his books are excellent!) address solutions you can benefit from. Now is a good time to make the changes necessary to improve your health. I quit smoking because I got scared. Fear is a great motivator. There's alot you can do, but I would start by eating fresh and natural foods, drinking water with lemon, cutting back on meat, and doing lite exercise everyday. You're young and should bounce back quickly. Good habits now will serve you well in the future. You're on the right track!! This is the best website in the world for improving your health.
Best wishes for good health,
P.S. While you may have parasites, I think your problem is one of acidity due to diet. parasites thrive in an acid environment..die in an alkaline (opposite of acid) environment. Best way to get rid of them.