you might try adding 5-HTP to the mix. i had the same issue, after taking melatonin – i'd fall sleep, but wake up a few hours later. pretty much every night.

right now i take 1/2 of 2.5 mg melatonin (sublingual) with 50-100 mg 5-HTP, ideally 30-45 min before going to bed.

adding 5-HTP was A MIRACLE ! after just a day or two i slept very soundly and had AMAZING dreams – we're talkin 2160p 10.5 THX Lord of the Rings epic trilogy with you playing lead role. those first few weeks i even went to bed earlier just so i could dream longer. :) prior to that it had been decades since i remembered having any dreams. (warning though, i've told several friends about it – after they tried it they had to stop because the dreams were too intense.)

i read about 5-HTP in this book i borrowed from my chiropracter: http://smile.amazon.com/5-HTP-Natural-Overcome-Depression-In... basically it states that melatonin is only part of the sleep equation, seratonin is the other part. your body can produce seratonin from 5-HTP (which is the chemical in turkey which makes you drowsy).

also:

staring at a computer screen can really mess with your sleep – due to chemical imbalance with these hormones. to help as much as possible, i installed F.lux on all of my computers.

i also recently added Modalert to my daily routine, but that's another story...