ds was going down at 7.30/8.00 pm(with some difficulty occasionally)until 2 wks ago.suddenly, he has been waking at 8.30pm screaming for no apparent reason.thought it was teething,used calgel,calpol.no effect.thought he was hungry, fed him,no effect.a far as i am aware nothing has changed.he is then very sleepy at 11.00 pm and goes down till about 5.naps are okay.any suggestions?