In my mind, I've always thought high levels of oestrogen cause nausea . That left me confused when I suddenly developed it at a time when I knew my oestrogen was low (had a blood test the same day, by coincidence). Anyway, fast forward many months, and I am now taking the pill. Over six months, my symptoms have all but disappeared (touch wood). However, recently, during the pill free phase at the end of each month, they have returned with a vengeance. Main symptoms have been headache ... and severe nausea. Whilst it's annoying, it has proved that in my case, it's lack of oestrogen, not an excess of it, that makes me feel sick.