Hi dangermouse - if you are taking the pill then you should no longer be ovulating as it suppresses the cycle so your oestrogen should be fairly constant although it could cycle a little (but nothing like before) if you are on a very low dose one. Progesterone should be completely constant subject to your digestive system! Or rather almost all of it will be synthetic from the pill and you will have very little of your own progesterone. Possible a tiny bit from the cream.
If you are nauseous then the pill probably doesn't agree with you and both hormones are synthetic so maybe not comparable with how you feel on your own hormones.
Also - as we have seen women seem to react to the changes in hormones very differently - some women feel nauseous with very high oestrogen and some with very low oestrogen. Some from progesterone - I don't think it is at all universal and I certainly do not agree that you need to add progesterone to balance the hormones in that way - except to protect the uterus.
For example during pregnancy, our oestrogen and progesterone levels are both extremely high. Some women feel nauseous for the first 3 months and some all the way through pregnancy - now that is a state where the hormones are well balanced because each is doing a different job for the pregnancy.
Walking the dog if you feel nauseous the week before and during the bleed then it is most likely in your case due to the fall in oestrogen because that is when your own oestrogen is at its lowest. Most women get some temporary progesterone withdrawal symptoms also just before the bleed and sometimes for the first few days - but this does not mean progesterone is needed - it is just the physiological changes which occur when the progesterone (that is no longer needed if you are not pregnant) leaves the system.
Pam Madra - I don't think you need progesterone in peri-menopause to help with nausea - but in any case if you are taking oestrogen and you still have a womb you will be taking it anyway in fairly high doses.
Hurdity x