Increasing the progesterone is usually a good strategy for problem bleeding.
BMS guidelines recommend ; the use of 200 mg as a continuous preparation and 300 mg as a sequential preparation should be offered if using high dose estrogen(24, 39-42) or, if unscheduled bleeding occurs with low to moderate dose estrogen.
As you are having unscheduled bleeding on 75mcg which they consider moderate, I would try the 200mg a night dose.
This does not require investigation as postmenopausal bleeding as you are still menstruating.