Five cycles in a row of bleeding before period, but hormones normal

It has now been five menstrual cycles in a row of bleeding brown blood for 5-6 days leading up to the start of my period.

(30/F)

-I had my hormones checked and they are normal. (Checked on day 20 of cycle)

-Thyroid results normal

-I also had an MRI and there was nothing that would explain this.

I am at a loss, and feel exhausted. Can anyone please help, share experience, ideas, etc?

Thank you in advance.