Hi dear, you have given such a nice account of your medication however, you should have mentioned how many days before the expected menses you have started Primolut N
tablets. If you have started less than 7 days, the dose is different lest the risk of failure.
Little spotting you are having is break through bleeding. As you have rightly mentioned, if you double the dose, this spotting will spot. Again if the spotting starts after minimizing the dose, keep yourself on double dose till you want to postpone your menses.
The withdrawal bleeding you will have after discontinuing Primolut N will be much lesser than your usual one.
I hope you got your query solved.