On average, the extent to which the uterus lining grows in response to oestrogen is dose dependent ie more oestrogen = thicker lining. Similarly the amount of progesterone needed to thin or shed the lining is also dose dependent. Higher doses of progesterone for longer will be more effective (on average) than lower doses for shorter duration - but depends on the dose of oestrogen too. The licensed doses of progesterone in all combi HRT products are worked out to be effective for the majority of women - on average - as a result of studies.
As has been said - if you still have a cycle ie ovulate - this can override the HRT cycle. If you are post-menopause then you are pretty much just getting hormones from the HRT.
So why would one not bleed?
The main explanations I suggest are: 1. the lining has not built up sufficiently to be shed (due to lower oestrogen dose or absorption 2. the progesterone dose has thinned the lining during its use so that there is no lining left to shed 3 . the progesterone is not being absorbed. If 3 then the lining would continue to build up until it became too thick and then would be shed randomly and spontaneously as abnormal bleeding.
If using 200 mg progesterone vaginally for 21 days, unless the lining was thickened under previous oestrogen doses - this should be more than sufficient to shed any lining that has built up, because it is greater (longer duration) than the licensed dose. The other explanation is that you haven't absorbed it, though the capsules are designed to be used vaginally as well as orally so no particular reason why not.
It is better to use for a longer duration than shorter - research has shown - ie the 7 days is not advised as it does not give enough time for the progesterone to do its job - but under supervision of your doc, of course this can be tried.
Of course we are not identical machines so what is happening in your case I can't say ....
Does that help?
sheila - I'm not sure what you mean by this "I haven't heard that using for longer helps." ? ie helps what?
Hurdity x