Re: What the......?
The fact that you had a good morning is HUGE! it implies that your baby can get a good latch- perhaps she is finally growing enough that she can achieve a deeper latch with less effort. Or her tongue mobility is improving. Something positive seems to be going on, anyway!
It's very common for babies to become increasingly fussy and difficult to nurse as the day wears on and the baby gets more tired out. If a mom is having issues with supply, those issues tend to be worst in the afternoon/evening and least troublesome in the night/morning, due to natural fluctuations in the level of Prolacting (the milk-making hormone, which tends to be most abundant at night and least abundant in the afternoon/evening).
I am sorry the day turned so frustrating, but focus on the wonderful morning you had!
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"