3 week old used to sleep on back ok when finally got asleep (sometimes took 2 plus hours) but now since age 2.5 weeks baby constantly squirms and wriggles and wakes up grunts a bit when placed on back. I was worried about reflux but during the day baby will sleep on back eventually, at night not at all, every 30/45 mins I am trying to settle. If put on front or held will sleep more easily. Pls help !!!