Ds2 will be three in two weeks and is too big for his sleeping bags. We tried to move him to a duvet, and while he went to sleep happily, his sleep was so disturbed, lots of crying, sweating, waking all night long which he hasn't done for ages. After the third night we caved and squeezed him back into his sleeping bag, and he's slept a dream! Should we just get the next size sleeping bag (3-6) or persevere with a duvet? Have anyone else's children had this trouble with a duvet?