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I found this on the miscarriage support website:
menstrual cycle
You may resume a normal cycle immediately with the next period 28 days after the miscarriage but there is a great personal variation,
and it can take up to 6 or 7 weeks for your period to return, especially if you had a "natural" miscarriage (i.e. no D&C or tablets).
It still may take a few cycles before your regular pattern is re-established.
Ovulation can occur 14 days after a miscarriage so you may wish to take precautions.
I think everyone is different on how their AF start again. I know this is a worrying time, I would go to a dr too and see what they say