Enfamil A.R. Bottle teat size.

Mine also when 6wks old but PD just recommend Enfa Gentlease so now going 4mths still use the slow flow teat since born although I buy 240ml which comes with med flow teat but both bottles and teat not yet use. Still drink less than 150ml and med flow teat flow too fast as there are milk flow around mouth area. Hegen got a thick feed teat which is a Y shaped especially for thick liquid, maybe you can check with Hegen whether is it suitable for 2mths baby otherwise you can make the teat hole slightly bigger but try it bit by bit.