Does anyone else have this? It seems to be a pattern I have developed over the past 12 months or so. The week following the end of my period I invariably feel absolutely rubbish - weak, tired, head-achy, a bit kind of light-headed and brain foggy. I thought the most obvious reason might be low iron but I don't have especially heavy or long periods I don't think. I had my bloods done a couple of years ago and all seemed fine (thyroid, iron, etc). I'm 45 so I guess peri-menopausal but my periods are still totally regular and no other changes really. I'm fairly fit and slim/thin - only mention that in case it has a bearing on iron or anything. Anyone have any ideas?