18 month old suddenly waking at 5:55 without fail. Used to sleep until gone 7. I’ve tried everything in the last two weeks and nothing is changing it! Slightly earlier bedtime, slightly later, more exercise, more food, less food, more drink and less drink etc. The room is pitch black so it’s not a light issue. I’m a lone parent and this feels like the worst thing as it’s making my days seems even longer. Please help