Minnie123 - hi and welcome to MM
Do tell us more - how old are you? What HRt are you using?
If you are on a continuous HRT ( which I assume you are) then some breakthrough bleeding is common in the first 6 months. When you say “a periodâ€, is this a period as you used to get in your reproductive years? OR is it just some light spotting or bleeding?
Bleeding on a conti HRT often occurs in the first few months as the body is adjusting to the hormones - your oestrogen levels have increased ( you may have been very oestrogen depleted before starting HRT) and now your womb lining is shedding a little and this should settle in time.
If you are feeling generally well then I wouldn't change anything but if the bleeding continues beyond 6 months or starts to get heavy, then you need to pop to the GP and they will probably send you for a scan.
I suspect things will settle in the next 2-3 months. DGx