My 17 month old had a couple of days of illness where woke in night, resettled quickly though. Since then (fully recovers) and for last 5 nights he wakes between 4:45-5:15 screaming the place down. Nothing calms him apart from getting him up. He gets extremely angry if I offer him milk, try to sooth him, leave him to it. He's ok if I get him up although exhausted and grumpy. Before this he generally slept until 6:30ish. He goes to sleep around 7 and normally naps 1-2:30. Any tips?