That is so true. I too am a recent sufferer of a SAH and so often think "that's easy, I'll be fine doing that", followed by doing about a quarter of what I intended to do, followed by a 3 hour nap.
I'm slowly learning that I must take it easier, which is admittedly hard when life is still carrying on at the same pace as before, you just have to make allowances for yourself, it's going to take time and patience (or so I've been told).
I also get the sharp headaches when i'm stressed, everything's still settling down in there really, so I suppose these things will still be happening
all the best,
Kay