I am experiencing slow thinking, moderate headache of gradual onset, lasting > 3 hours, on the front side, that gets worse with psychological stress, being tired, that is unaffected by bending forward, changes in sleep pattern, sneeze or cough, exercise,

Many possibilities: Most people get a headache at some time, such as from colds, infections, lack of sleep, too much driving, long hours on the computer, stress at work, etc... Over-the-counter treatments include Tylenol, Motrin, Aleve, Excedrin, and their generic brands. A bad or increasing headache, recurrent headache, weird headache, or one with other worrisome symptoms can be checked by one's primary care doctor.