I think this discussion is getting sidetracked by the fact that there are multiple definitions of “good”. They are related but not entirely equivalent.
There is “natural good” that deals with how God designed creation. And there is a more specific “moral good” that refers to our proper use of free will to choose “good” over “evil” or to choose between multiple “good” possibilities.
Breastfeeding is a natural good. We know it is the ideal for both baby and mother. The decision to undertake a course of action in order to prevent/delay ovulation (as opposed to taking that same or a different action for other reasons) gets into the moral area.
There is “natural good” that deals with how God designed creation. And there is a more specific “moral good” that refers to our proper use of free will to choose “good” over “evil” or to choose between multiple “good” possibilities.
Breastfeeding is a natural good. We know it is the ideal for both baby and mother. The decision to undertake a course of action in order to prevent/delay ovulation (as opposed to taking that same or a different action for other reasons) gets into the moral area.