Check out melatonin and/or valerian. Melatonin may cause a bit of next day grogginess but not as bad as diphenhydramine (generic Benadryl). Valerian may also help if there's any anxiety associated with the insomnia. If these don't help then give Benadryl (diphenhydramine) a try. If that doesn't help talk to your doc.
Watch your caffeine intake as well. Don't eat right before you hit the sack. Have sex (if you're married)...