It should be adequate for endometrial protection particularly with vaginal delivery, however whenever anyone takes less than the guidelines (which were developed to make sure even the highest risk women are protected), getting a scan now and again is sensible.
Cramps are not a cause for concern and likely to settle as your body adjusts, however as sequential hormone therapy was originally designed to mimic a menstrual cycle it is not unreasonable to expect some of the same symptoms.
