I agree that not every woman is the same. And there’s nothing wrong with wanting to be happy. But several things is wrong with your reasoning–and I bolded those things stood out to me. For one, you assume that a woman who is the mother of more than 2-3 children must be a SAHM. Those are separate decisions. I know mothers of large families who have careers, and I know families where the woman works while the dad stay at home, and I know women who stay at home with small familes.
There was a time when my husband and I only wanted 2-3 children. Very few people go from 2-3 children to 6+ children overnight. Babies usually come one at a time (sometimes two, rarely 3). Some women cannot have more than 0-3 even if they want and actively try to have a large family.
Once we decide to marry, we’re suppose to be open in our marriage to the number of children that God wants us, not just the number than we decided we wanted earlier at some point in our life. Our personal happiness isn’t always found in getting what we want; sometimes we really have no idea of what will make us truly happy, but God does.
Plus, the nursery rhyme character, Mother Hubbard hardly reveals the image of a happy SAHM. Since Old Mother Hubbard was old, maybe additional pregnancies weren’t a concern. But if it was, since her cupboard was bare and she didn’t have a bone to feed her dog, I’d say she had just reason for avoiding pregnancy, (if she and her husband prayed and agreed on it.) The rhyme doesn’t say if Mother Hubbard had a large family or not, and she may have been retired from a career for all we know. Do you have Mother Hubbard confused with the Old Woman Who Lived in a Shoe? That lady had so many children, she didn’t know what to do! Again, hardly the image of a happy SAHM. Not a happy stay-in-the-shoe mom either. She would have “just reason” for avoiding future pregnancies, (if she and her husband prayed about it and agreed.)
It seems that your image of mothers of large families is based on old nursery rhymes and stereotypes of us.