What could be happening if i can't seem to sleep more than 4 hrs a day and i'm only 29yrs old?

Chronic Insomnia: Is caused by many factors:an abnormal mthfr genotype (low melatonin production), anxiety, sleep apnea, mania (from bipolar d/o), working night shift (or other strange hours), too much caffeine/stimulants taken late in the day, or depression. It can also be "idiopathic"-nobody know why. Very safe meds with short half-lives ; little side effects are helpful. Must take right before head hits bed!