Can you get a copy of Elizabeth Pantley's No Cry Sleep Solutions (Dymocks etc)? She describes the method of weaning off the breast to sleep. It takes time and effort (but any method will) and it involves allowing your son to feed until very sleepy, then detaching. He will cry, then you reattach and keep doing this until he is asleep. So in effect, he is 'dropping' off to sleep without the nipple in his mouth. It is better described in the book! You can also (when he is off but asleep, but 'rooting' for the nipple) VERY GENTLY close his jaw to stop the sucking motion when he is off. You repeat this every feed, every day until he is asleep without the breast. It may be that you still hold him to sleep, but then you will have to work on getting him to sleep in the cot with you settling him. the book also has lovely settling strategies that don't involve you leaving him to cry.