My 6 months old sleep routine sudden changes, he now sleep in late like 11pm plus and sleep through he night until 9am plus to 10am plus. He is not waking up for milk in between I have to feed him and he will continue to sleep. During afternoon he will be very active but at night he got problem sleeping and that cause him to sleep late .. I try to comfort him but he still don't want to sleep. I guess is due to him teething. He keep bite stuff put inside him mouth and pull in and out like rubbing his gums and bitting on it. I hope it will be normal soon. He used to sleep at 7 or 8pm. And wake up at 7 or 8am.