Depending on your waking routine and your work daily, it could be not only from worry and stress but not on a early busy routine or diet.
Let me explain, if you are up at 6 am - like I am - and drink one cup of coffee during the routine of getting ready in the morning, it is best to start on your day as soon as you hit the floor rather than dragging your feet, sitting with your coffee/paper/morning radio or tv, and then starting your day. As soon as you wake up, hit the shower, even though you may have done so before going to bed, just hop into it for about 5 minutes. Then go get your coffee. While you are running around and getting dressed make sure you have a high protein and fruit breakfast. 4 oz of protein and 1/2 cup of fruit. Why, you ask? This starts your blood flowing much quicker and that way you are not so sluggish as you trod yourself off to work or school. In a couple of hours eat a 2 oz worth of protein plus 1/2 cup fruit, to keep the calories going. If you want, a good multiple B vitamin and a cup of green tea or a green tea capsule to boost your energy levels at that time. By the time you have eaten lunch, another small snack, and finished your day, instead of going straight home and plopping on the couch, sit outside instead or take a quick walk if possible. Your not looking to work out, just a chance to clear your mind. By the time you have eaten some dinner and relaxed in your comfy area (where ever that may be ;) ) you should have no problem falling asleep.
Our problems with sleeping patterns and our mind and body's idea of continuous energy stems from usually from a poor routine and diet. We are always running here and there, grabbing whatever is easy to throw down our throats or walk and eat at the same time and never thinking why our heads hurt, our stomach may hurt, why am I so tired during the day but can't fall asleep at night. This is why. The more activity and balance in comsumption of "good" calories during the day (or whatever shift you work this idea works on any schedule) , especially the earlier in the start of your day, the better physically or mentally you will be. By the time you hit the bed, sleep will come easier. If worse comes to worse and you still can not sleep I would look to a natural sleep aid such as Kali recommended as well as maybe adding some valerian root - extract, tincture, or capsule - about and hour BEFORE you are about to go to bed. This means take it while you are reading or watching tv and when you are ready to lay down you should have no problem falling asleep. These are non habit forming BUT it is best to start evaluating your daily routine and try to modify your eating habits and your routine. It may take you a week or less to get the hang of it, but it will work and you will not need to use anything to help you fall asleep. Your body's own natural processes and chemicals will end up balancing out. Benadryl is safe but it can be habit forming and could cause you to have overly dry sinus cavities which can result in nose bleeds, sinus headaches, and even a soar throat if taken too often.
I hope you will soon have sweet dreams again.