My first thought was Lullaby by Got7 but I don’t think it’s actually fitting other than the title

This is the one my mom used to sing to us, although there were some more. But this was the one that was specifically a luaby
Also I’m not much help, I’ve struggled with sleep for ages but before medication I really couldn’t find ways that helped enough. But I do know that sleep hygiene and such are important, and that things we do in the day also affect sleep. For example, using electronics close to bed or making a habit of using our bed just to chill on, from what I remember it makes it harder for the brain to associate your bed with sleep and not just other daily activities. There’s more too ofc. Idk if you’ve tried those already, or if you know they won’t help, but if you haven’t and want to try they can have an effect on your sleep ability. Can’t guarantee anything though ofc.