It happened to me a couple of times, but I don't remember which pill I was on. I skipped two in a row, but hadn't had sex at all when the first period didn't arrive on schedule so didn't worry. Saw my GP when the second one didn't arrive on schedule, and he decided that the pill I was on was too strong for me and changed my prescription. Got to the third... and it arrived on time and was a right shocker - started the new prescription after that one and then everything continued as normal. It sounds like something similar has happened for you, but if you are worried, see your doctor and get a blood test. It might just be a case of a different pill would suit you better.

BW