It's extremely unlikely to be anything worrying but you probably have built up quite thick lining which needs to shed.
Make a GP appointment and ask for something to stop the bleeding if necessary such as tranexamic acid, a blood test to make sure you aren't anaemic, and either an increased dose, formulation or route of progestogen going forward.
A scan should also be done to exclude anything requiring specific treatment. Also ensure your smear is up to date.
Your estrogen dose is not necessarily too high - the correct dose for you is the one that relieves your symptoms, however oral micronised progesterone isn't always strong enough to keep the lining in check and some women do need either higher doses or to take it vaginally, or alternatively a stronger progestogen such as the mirena or an oral progestin.
