
Well, I think you might want to visit a doctor who is familiar with
sleep disturbances, because antihistamines only help induce sleep when
they're used intermittently; they lose their sedative effect if they're
used on a nightly basis.  Their anticholinergic effects (drying of secretions,
relaxing effects on smooth muscle) can be problematic in some people, such as
those with glaucoma or prostate enlargement.

Antihistamines like diphenhydramine (Benadryl) or doxylamine (Unisom)
are potent sedatives which are useful occasionally.  Chlorpheniramine
(Chlor-Trimeton) is said to be less sedative, but 8mg seems to work
well in some people.  Both chlorpheniramine and doxylamine have long
half-lives compared to diphenhydramine, and so may produce a residual
hangover or "drugged" feeling the next morning.
