A problem I have when trying to sleep is that I usually get into camp late and still have lots of blood pumping and need time to relax before going to bed.
There are a few 'natural' things you can do to help you go to sleep. I am a huge hydration advocate and believe that drinking water can fix nearly anything. I have found that drinking a half liter to over a liter of water right before bed can really knock you out.
changes in your dinner or nighttime snack habits could also help you sleep- look for foods high in tryptophan and melatonin. Chicken, Turkey, and Tuna are common packable meats you could eat that are high in tryptophan. taking a multivitamin in the morning would help make sure you have proper nutrition to metabolise it (especially B6 for tryptophan). Sadly, tofu is extremely high in tryptophan, but its tofu. Some nuts and seeds are a good source to, like pumkin, soy, and sesame.
lastly, hammock camping helps me sleep like a baby.
Good luck

