It sounds like you are waking up in the light-sleep phase of every sleep cycle. I've never had insomnia that bad, but when I'm stressed, whether it's positive or negative stress, I wake up very easily at the slightest sensory input. I keep my bedroom as dark as I can, but even then, sleeping with a soft sleeping mask and good ear plugs will help keep me "down" through those phases. They can make it slightly harder to fall asleep, but once I'm asleep they help keep me there.

(And of course, limiting coffee and tea. I try to stick to just one cup of coffee in the morning, and max 2 cups of tea, pref green or white, before 3 pm.)