Hi Flamingo,
I have had sore large boobs at times on HRT and found that reducing the oestrogen dose helped greatly. I believe sore boobs can be a symptoms of either too much or too little oestrogen so it's a case of tweaking to see what suits you best and hopefully you will find the right level.
It's really important to make sure you take progestrone to ensure the lining of the womb doesn't build up too much as a result of the oestrogen you are taking, so personally I wouldn't stop taking it while having the oestrogen. If you don't get on with the progesterone you need to speak to your GP as there are other options.
Hope you find the right balance soon