Possible reasons include, 1. dehydration leading to thick ropy saliva; 2. New filling / new teeth coming (usually wisdom tooth in your age); 3. Salivary gland stone ( like
kidney stone) ; 4. Infection or blockage of saliva duct. 5. Enlarged tonsils, Plus there are many more. Before you jump to any conclusion yourself, try to rule out these simple causes, drink lots of water to increase watery consistency . Watch out for any redness or swelling. Visit your doctor once