sebx, welcome to MM.
I can understand why it has come as a shock, it did to me too because I was also young - the doctor kept saying "you are very young". I was not expecting it at all and only found out after a blood test although I did wonder why my internal thermostat was not working very well.
Being younger makes it all the more import to use oestrogen replacement because otherwise it is a long time to go with hormone deprivation which can cause all sorts of problems in later life. As others have said, the benefits of HRT far outweigh the risks particularly at your age. I would recommend taking HRT transdermally (I prefer the gel) but you will also need progesterone if you have a womb and I would recommend Utrogestan because it is bio identical and has far fewer side effects, particularly when taken vaginally. It is worth noting that the risk element of HRT is in the synthetic progestin content, not the bio identical oestrogen. Synthetic progestins have some unpleasant side effects for some people and they undermine all the good work that the oestrogen does.
I have been around the block on this one and this is the best HRT regime in my opinion. I only wish I had started with it straightaway and not wasted my time on other medication that didn't work.
I hope that helps.