Ohh, feeding, you only gain balance on that one retrospectively, I think. I completely sympathize with anxieties over breast feeding, slow weight gain, etc.
Your instinct tells you to love, protect and nurture your baby. The details have to be learned. We try to measure our success against norms such as weight charts and baby books, but the babies don't always seem to conform (my best HV said, 'Remember she (DD1) can't read the book yet'). By the time we've learned how to manage one aspect of our babies' lives, they've moved on to the next stage.
I'm not very helpful on this, as I don't think I was brilliant with babies, and just sort of muddled through it (both times). With several years of distance, though, I am incredibly rational about it all, as both babies (9 &12) are still here, eating, sleeping, growing and learning. I have learnt to be assertive when I'm sure there is a problem, and to be more confident in my parenting style and choices. It's a very long haul, though. Keep counting the grey hairs.