Hi SiffyByng. :) I have this too, but didn't know it until we had already started topping up with formula after dd was admitted for dehydration at 6 days old. Like you, I had no breast changes in pregnancy and no sensation of milk coming in after my daughter was born, though I did have colostrum and some milk. It sounds like your supply is much better than mine was, because there is no way we could have gotten to 6 weeks with dd being "healthy and alert, and developmentally strong" as you describe your daughter. When we brought her back in to hospital, she was lethargic and visibly dehydrated (cracked lips, flaky skin etc). Maybe that's an indication that you're more likely than I was to be in the 33% for whom ebf works out?
Even with my very poor supply, we went on to combo feed to six months. I do wonder whether my supply could have been built even a little bit more if my condition had been recognised before the point where dd was sick from lack of milk. By the time that happened, I was just grateful for the formula and relieved to finally be getting some dirty nappies and know that she wasn't starving. When we brought her home from neonatal, we were reliant on the top-ups and my supply never picked up despite endless skin-to-skin, suckling, pumping, fenugreek and domperidone. I did, however, manage to retain a reliable-if-meagre supply until about six months, when she started solids and grew increasingly impatient and frustrated at the breast.
I just wanted to say that given the very real obstacles in your and dd's way, you are doing an absolutely fantastic job to still be ebf at 6 weeks. It is hard work and it's physically and emotionally exhausting (and we didn't have a tongue-tie!). For me, no matter how much I rationally knew that it wasn't my fault that I couldn't provide enough milk, that was a very difficult thing to internalise and let myself off the hook about. If I'm honest, I still haven't, entirely. I'm not surprised that you feel shattered and demoralised, and the conflicting "expert" advice can be maddening.
I do see now that the lactation consultants, midwives, nurses, hvs and gps couldn't win: if they told me there was still hope and I should keep trying, I felt that they didn't really believe that the problem was something I just couldn't fix, and I would therefore be 'failing' if I accepted that it wasn't going to happen. If they told me it wasn't going to happen and formula would do just fine, I felt that they didn't respect how important breastfeeding was to me and that they were devaluing something I'd worked so hard to maintain.
It's a tough in-between position to be in, and it's made tougher by the fact that so few people have even heard of tubular hypoplastic breasts. I felt very alone in those early weeks (despite the ever-supportive presence of my lovely dh) so I just wanted to share a bit of my experience to let you know there are others around who have dealt with similar situations.
I wish you all the luck in the world. Combo feeding worked out great for us and is by no means the end of the world, but given how (relatively) well things have gone for you in the first six weeks, I really hope that the tongue snip makes all the difference and you land firmly in the 33% club :)