Tiredness is the symptom everyone expects and nobody checks
It is the commonest thing women report after a birth, it travels closely with low mood, and it is also on CDC's list of signs to be seen for immediately.
Tiredness is the most reported physical problem after a birth. 67% of women in the first three months in one study. 69% in the first six months in another. It is so expected that it has stopped counting as information.
Two things follow from that, and they point in opposite directions.
The first is that being exhausted is not a sign you are doing badly. It is what the majority report. If you are measuring yourself against women who look rested, you are measuring yourself against a very small group.
The second is that exhaustion is also how serious things present. Pooling 35 studies, nearly all of them of women, tiredness and depressive symptoms after a birth were closely correlated, r = 0.52. That is a strong relationship. It does not mean one causes the other, and treating tiredness has not been shown to treat depression. What it means is that the two should be looked at together, which is what the authors of that review recommended.
And then there is this. Overwhelming tiredness appears on CDC's list of urgent maternal warning signs, the symptoms it says to seek medical care for immediately, during pregnancy and in the year after a birth. The single symptom every woman is told to expect is on the federal list of things that should get you seen the same day.
"Can we check my blood count and my thyroid?"
"I am also low in mood. Please ask me about both, not one."