Zara - I believe that for those women who have had a hyster, using oestrogen alone can actually reduce your risk of breast cancer!!!! I know 4 ladies who have had breast cancer (one died), they all sailed throughout their menopause with barely a flush so didn't use HRT - so unless you have a close relative who has had oestrogen sensitive beast cancer your risks are very, very small and you may be more at risk if you don't use oestrogen.
I must also point out that at 52 you would be going through this whether you had your uterus and ovaries or not - it certainly wouldn't have been so sudden but the peri menopause stage can actually be the most challenging time for many women as we can go through many years of fluctuating hormones that bring all kinds of problems. It is often not till women are actually post meno and find a good balance of HRt that they really start to feel their flushes and night sweats are under control.
There is still much debate about the true risks of HRT but I also read somewhere that research now shows if women use HRT for 5 years in their fifties it can lengthen life by about one and half years - it will certainly help to prevent life limiting problems like osteoporosis and heart disease. Using oestrogen will also help to prevent vaginal atrophy and bladder problems and believe me you don't want to risk getting those menopausal symptoms too early. If you are getting discomfort around you vaginal area then some additional local oestrogen like Vagifem is a good idea.
If you can find the right amount of oestrogen that keeps your flushes etc under control then I think this may be the answer to your problems. If you were taking oral oestrogen then I could understand the gastritis but this is a very unusual side effect with transdermal use!!! I think the gastritis will be more to do with anxiety and diet - also do avoid NSAIDs painkillers like aspirin.
I have found that higher doses of oestrogen do give me some side effects and perhaps trying some Oestrogel and just using one pump per day, either morning or night, could be a good alternative for you. I've never needed a particularly high dose to control my flushes and I suspect, from what you are saying, that you might be the same. However, it is worth taking enough oestrogen, not only for reducing meno symptoms but also for the protective element, so ideally you should use no less that one-two pumps of Oestrogel or one sachet of Sandrena per day. If you need the two sachets then do stick with this - it's fine.
You seem very anxious about using oestrogen but I do hope we have reassured you that you are doing the right thing. Dg x