Some sleep problems don't arise because of worry or melatonin problems. Some are caused because your back hurts like stink. Truth is, some people get through general back pain or knee pain during the day because they're so focused on other things. But when trying to get to sleep, they feel the pain—and focus on it.
A simple over-the-counter anti-inflammatory medication can help—not specifically to get you to sleep, but to help alleviate the pain that's preventing you from sleeping. Take aspirin with a glass of water at least one hour before bedtime so that the acid doesn't have as much chance of refluxing up from your stomach to your esophagus.
Allergies can make sleeping trouble worse because of the congestion they cause. About 40 percent of people with allergic rhinitis have trouble sleeping. Over-the-counter nasal strips and sprays help open up everything and clear up symptoms like headaches, watery eyes, runny nose or new-onset snoring.
If you experience those symptoms and aren't aware of any allergies, search for the source in unexpected places. Some have allergies to gluten (wheat, barley, oats), which can lead to congestion and increase insomnia, as can allergies to detergents and the cleaning products you use on your clothes or sheets.
One note: Decongestant nasal sprays are addictive and raise your blood pressure. Saline or antihistamine sprays (or a prescription steroid spray) are better options.