My experience with YASMIN is that it might take 3 - 6 months for your AF to stabilise and fall into the "white area" - some women stabilise quicker, and can have a set AF after 2 months i.e. 28 day cycle starts on the right date (or what ever).
They do suggest for two months into using any BCP that you use another method of BC as well i.e. condoms.
The theory is that if you miss one tablet, take two the next day and use a condom for one week.
That is the theory - however if you are taking more than one tablet at once because you have missed several days, there is no real way to know if you are indeed "safe" and the rule of cautionary thumb is to use additional protection for the balance of the month.
YASMIN needs to be used for a long period of time to allow it to stablise in your body especially if you have other issues that might be throwing your AF out.
If you are struggling to take the pill each day, then possibly consider looking at the EVRA patch as an alternative.
My understanding (and I may be off the mark on this) is that Yasmin may prevent ovulation; however it may not do this reliably each month.
It works also by thickening the mucus around the cervix and preventing sperm from entering the uterus. The lining of the uterus is also affected in a way that prevents fertilized eggs from implanting into the wall of the uterus.
But that is my understanding .......... not sure if it answers your question though.