Difficulty with thinking is a terribly unfortunate problem to have, and could be a sign of other medical problems. For that reason, you should likely start with your primary care doctor, who will know you best and will have some sort of baseline established. He or she will be able to sort out what area or system is causing your problem, and order the appropriate tests to get you started on your road to feeling better. Your situation is somewhat more complicated than most, as your history of vitamin B12 deficiency could be adding to your problem, as well as your eustachian tube difficulties. Additionally, your past medical history would likely start your primary care doctor off in some sort of direction with regards to possible electrolyte abnormalities that could be playing a role. By checking some routine lab work and doing a physical examination including how you walk and the strength of some of your muscles and nerves, your doctor will be able to see what could be at fault and then recommend the appropriate specialist as needed.
This could ultimately include visits to specialists such as a neurologist
, a sleep specialist, an otolaryngologist (aka ear-nose and throat surgeon
), or an endocrinologist
as well as others. Please see your physician, as changes in thinking can be signs of something more serious.