My elsdest son was exactly like this...and would anyone listen to me? No! He could go hours without any milk and then take about 2oz. He regularly took about 11 oz in one day, yet as he still managed to put on weight every week, the Dr and midwife weren't interested. It totally preoccupied my life and I worried constantly about it. I used to wish that the bottles would squeeze!I tried him on evry type of bottle and every type of teat as well. I did wean him at 3 months because of this and once he got a taste of proper food, he gave up drinking from the bottle completely!! So I used to buy the baby food and add milk to it...even if it was an 'add water' food, so at least I knew that he was getting plenty of calcium. I also gave him yoghurts and anything that had calcium in it at all. I never knew of another person who had this problem, so it is nice (for me) that it is not a completely unique situation. It was so weird having another child years later who drank a 12oz bottle every 2 hours!
My eldest is now nearly 14 and the weaning guidelines were 4 months then but sometimes you just have to do what you feel is best. He is a healthy teenager, who eats and drinks all kinds of foodstuffs...but you would never catch him drinking a glass of milk to this day! Good luck, you are not alone. I would go with my gut feeling and don't worry. I wish I had spent less time worring about it...the time passes and there will soon be other things that he will worry you with, believe me!! lol
kerris x