@Joarden There's nothing icky about talking about menopause, revolting as the actual process may be.
I'm assuming you are young enough that your periods suddenly stopping comes as a surprise? Periods stopping and menopause, when it comes to breast cancer treatment, are not necessarily the same thing.
If you are having chemo, it's absolutely normal for your periods to stop. If you are ultra-stressed, ditto. If you are taking tamoxifen, you are likely to have menopausal symptoms, though your normal cycle might return after your five year sentence.
It sounds like you need to have a good chat to your oncologist/GP/breast care nurse. These are the sort of things that often get overlooked when everyone assumes someone else has talked to you about it. MXX