Why do I get dry mouth? Its so bad that I have to be shewing gum or get a zip of water just to get it moist

Xerostomia. Dry mouth is usually from medications smoking or some diseases etc. If you have this, it will affect your teeth gums and needs professional help. See your dentist chuck.
Check with MD first. This is an important question because you are much more likely to get decay with a dry mouth. See your md to see if this is a symptom of an illness or if it is caused by drugs you are taking. If nothing can be done for it then see your dentist for ideas to keep your mouth moist and decay prevention.