Yes - the feelings of failure are a mental health issue. The depression I had, the worry, the wedge it drove between DH and I - all because DD had an undiagnosed tongue tie, failure to thrive and was hospitalised.
Not once, out of the over 40 NHS HCPs and breastfeeding supporters I saw, did anyone look at me and say, "You know what, for this Mother's mental health it would be better if she formula fed." Just constant expressing, different timetables, different latching techniques, inconsistent advice and guilt, guilt, guilt.
I am now pregnant for the second time. DD is four. I can barely talk about her early weeks without bursting into tears. The moment there are any issues with breastfeeding, I'm getting the formula out. I can't do that to myself again.
Failure to breastfeed should have a fucking huge red flag for PND that is waved in the faces of all HCPs. If it's a choice to formula feed, then it's fair enough, but the number of women who feed their baby and feel horrendous about it, is a significant issue.