Have you tried melatonin? It's natural hormone and helps to regulate sleep cycle. It worked for me at least. I think you can get it without prescription in most countires.
Also i've heard that using computer at night is one of the common causes of insomnia so if you have to use computer at night (try not to) i would recommend you to to download this free program called flux which makes the screen darker. It gets some to to get used to it but i'ts worth it.