Alright, hot flushes are definitely a sign of hormonal fluctuations. If you have just had a hysterectomies with ovaries left inside, then hormone replacement therapy till the ovaries are functional is not required, however, after ovarian menopause the ovaries cease to secrete the required amount of hormones necessary and the need for HRT arises.
If you had a hysterectomy with oophorectomy, meaning the ovaries were taken out, then I do not understand why your doctor advised against HRT since, without the ovaries, HRT is required.
At this point in time, you need to get your hormone levels done, visit your surgeon and have yourself assessed. You might need to be started on some sort of hormone replacement. Just the required ones and not the whole spectrum of hormones.
Let me know if you have further questions.
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Wish you good health.