sleep

my lo is 12 weeks old and has been co sleeping with me from a few days old because of it being easier for bf etc but now id really love to have my bed back. the only problem is ive never tried to establish a routine and whenever he is in his cot he falls asleep for 10 mins and wakes up and cries. this is really frustrating for me and its probably because he is waking up and me not being there is upsetting him...what to do? also, what would be the best sort of routine for a 12 week old? something easy and stress free you could recommend? i really wish my lo had some sort of "set" sleeping times. hes all over the place and it really is tiring xx