Insomnia

Does anyone have any tricks that work for them to get to sleep quicker? It regularly takes me 4-6 hours to get to sleep despite feeling absolutely exhausted all the time. I lie there trying to get to sleep not doing anything, in the dark and with my eyes closed. I've tried sleepeaze tablets, melatonin and taking the maximum dose of cough medicines that are meant to make you drowsy (so basically every over the counter option), I've tried drinking alcohol, I've tried every variety of counting sheep/repetitive mental tasks, I've tried breathing exercises that I've found online,I've tried listening to calming music/ASMR, and I've tried reading a book before I go to sleep and I'm basically immune to all of it. Nothing has had the slightest effect. I've told doctors and they won't give me any proper medicine because I'm young/healthy and just suggest techniques like the ones above that don't work for me. Does anyone know what else I could try?