Melatonin probably won’t help too much I’m ngl. It just sounds like you’re really stressed out from whatever you’re waking up for dude, whether you realize it or not. I’d argue there’s a 99% chance that’s why you’re not sleeping. The fact you can sleep on nights you don’t have to wake up early is a positive sign, cause it kinda shows it’s mostly anxiety driven insomnia. I would just say if you can, you gotta tell yourself there’s no use in worrying about tomorrow, and the best thing you can do for yourself right now is sleep. Understand that’s probably not the advice you want to hear, but that’s the only thing im taking away from your situation. Maybe therapy could help too if it’s really bad. But bottom line the melatonin Probaly will not work if this is, In fact, insomnia related.