Anyone using the MAM anti colic bottle? The formula starts off with no bubbles, but when he starts to drink, so many form! How do I avoid that?! And I don't hear the bottom of the bottle venting. I just hear air from the Nipple when he sucks. Not sure what I am doing wrong or if that is what the bottle should be doing. I tried unscrewing the bottom a little, didn't do anything. Thanks!