According to NHS Choices, "Insomnia can be triggered by a number of possible factors, including worry and stress, underlying health conditions, and alcohol or drug use.
Sometimes it's not possible to identify a clear cause."
I found this video on YouTube about guided meditation to help me sleep. And it really does. Of course, I do need to give the video and myself a chance - I gotta listen to it mindfully and not allow myself to be distracted by my thoughts. Halfway through this guided meditation I get so relaxed and fall to sleep. I really don't know if it will work on you guys, but you wouldn't know until you try.
So get yourself in your PJs, in a comfortable position on bed, and listen to this.