You'll tend to wake up whenever you are in a habit of waking up. You don't have much control over that. What you do have control over is the time at which you lay down. So shut the computer and TV off, turn out all the lights (the darker the better) and go to sleep. If you have trouble, then take a 200-400mg dose of melatonin and a bit of Mg about 30-60 minutes before going to bed. You can operate with reduced sleep, we often have to due to uncontrolled factors. You'd can't thrive on it though. 7 hours really just isn't enough, especially when you factor in your training.

Among other things, sleeping more will boost your testosterone and growth hormone production while reducing cortisol. It works wonders in terms of reducing belly fat, not to mention improving recovery which allows more/better training. You can often cheat on your diet and workouts without too many issues, but you can't cheat your sleep. The order of importance is sleep-diet-training.