ds 19weeks old is such a wriggler, each night I put him to bed in his cot, in a sleeping bag with his feet at the end of it. within minutes he is on his front and then he is off wriggling up the bed, he has nearly bashed his head at the other end a couple of times. I am slightly worried about him escaping onto our bed then falling off ( cot has one side removed and pushed up against ours for easier night feeds) so other than velcro 
any suggestions to try to keep him in the right place ?