I guess I have the exact opposite problem. My LO has taken bottles occasionally from the age of two weeks and prefers the breast, often violently refusing the bottle when he is in a time of need or having one of "those" days.
One thing I did was never to increase the stage of the nipple on the bottle, always staying with the "slow flow" newborn nipple, even tho' he is now 8 mos old. He has to work just as hard to get the milk from the bottle so it is no more special than the breast.
Maybe if you made the bottle a little more frustrating by trying this, he would give up on it and use the breast more often.
Just a thought.