Should I Worried About The Delay In Periods After Unprotected Sex?

I've been taking birth control (lo loestrin fe) for about 5 months now. 12 days ago my boyfriend and I had anal sex for the first time and didn't use a condom. He didnt ejaculate inside of/on me, anywhere. So I really don't think anything could've happens. I know that it is common on lo loestrin to miss a period but I was supposed to start this past weekend and I haven't. I don't know if I should be worried or not...