Exhaustion - what can it be?

[doadeer]

Over past few months, a few days every month (usually before period which has suddenly shifted to 3 weekly) I have experienced absolute exhaustion.

Not sleepy really but just absolutely worn out. Like I've run a marathon.

I've just been for a blood test, waiting for results - other than obvious low iron. What could it be?

I am in early pregnancy about 4 weeks and feel absolutely all round unwell .. tired and lots of heartburn and gas. ... any advice as to when this might go away and perhaps more importantly is this normal ?