Simply stated, unless you have a condition that's organic in nature, which is unlikely, here are the reasons you might not be sleeping well:
- too stressed out to sleep well
- not tired enough/didn't get enough exercise while awake
- uncomfortable sleep environment
- psychological association of your sleep environment with daytime activities
- chaotic routine, no pattern to your sleep schedule
- allergies or muscular discomfort
It might take a serious bit of time and effort, but if you eliminate all the above causes you will sleep well. Unless something else stands out as being the problem, stress is far and away the number one culprit, so address that first. If you are not at least physically relaxed, don't even attempt to sleep.
Force yourself to get on a routine of some sort, and make yourself stick to it, at least 5 days out of the week. I'd advise staying away from habit-forming sleep medications. However, to improve your sleeping until it gets better and regular, try (one at a time) these:
1. melatonin
2. any anti-histamine based sleep aid (Diphenhydramine as an active ingredient)
3. valerian root
RedPill