It is always a shame when someone is so needlessly frightened of bleeding from an organ that was designed to bleed in the presence of ovarian hormones.
Firstly there is no evidence you even are postmenopausal - you said yourself you had been amenorrhoeic for many years on cerazette.
Ultrasound appearance of ovaries is not a reliable method of "diagnosing" menopause, particularly if someone is on suppressive treatment such as a birth control pill.
I would simply restart the cerazette and ask for a routine pelvic ultrasound for peace of mind.
There is no need to stop your hormone therapy, and it doesn't sound as if this is being particularly well managed by your clinicians.
Rather than being on a murine dose of estrogen due to the combined patch aggravating your IBS, which norethisterone is particularly known for, why not consider separate estrogen at a dose that truly serves you and try a different progestogen such as either micronised progesterone OR a double daily dose of cerazette as your progestin?
The latter is unlicensed but supported by the BMS based on evidence. This would also almost certainly have you bleed free before you know it.