Sorry that you have had this news. I had similar diagnosis in the 1990s. My Oncologist told me 'no HRT for you' but I really don't think that there is enough knowledge about who much HRT actually stimulates breast disease. I truly believe that if HRT was so dangerous then double mastectomy would be suggested, so that over-all, one can continue with HRT to relieve symptoms.
I had lumpectomy followed by a bone scan (over all body X-ray), 4 weeks radiation treatment - still here >wave<. I remember well the feeling os shock but once I got on with treatment I felt like I was doing something positive. My Surgeon told me that he didn't expect me to have any further pboelms in either breast, lymph glands were clean - but should I re-consider in future, he would of course do mastectomy. It never crossed my mind once I got going.
....... and breath. Make notes to take to your next appt. My Surgeon asked ro a list of worries every morning but he was so thorough that I never needed them!
tamoxifen made me feel very ill. It's an oestrogen suppressant but I wasn't warned that I would have 'flu like symptoms - after 4 months I had to stop taking it. I hadn't felt ill through the diagnosis and treatment so didn't want to spend the rest of my life feeling ill, when it was a 'this might stop the cancer returning' attitude. There are other drugs on the market but are they really necessary

. They come with their own problems. I don't know how much research is done as to whether they are necessary, if they actually stop oestrogen aggravating a potential disease or .......... as for the Consultant staying 'stop immeidatlye', it may be that's all the Medical Profession ever say without really knowing how much influence HRT has over-all.
Good Luck! I suggest that you look for nighties that can be done up at the front as pulling anything over your head will be difficult. Those muscles get tight after surgery and it's quicker and easier to whip open some ties when the Dr comes round to examine or if the Nurse needs to look at any dressings ;-). I had a running stitch above the nipple with a plastic bead at each end

. I asked 4 gold plated the next time ;-).

this too will pass. Take that list. Find those nighties which tie up down the front ;-) ..... let us know how you get on.