My DS 7 mths old wriggles in his sleep until he gets his head up to the top of the cot and then cries and wakes himself up because he is "stuck" (i.e. can't get any higher) and I have to "rescue" him (i.e. pull him back down to the middle of the cot) several times a night. Driving me crazy and sleep deprived! Any one else experienced this and any suggestions??