Stressing out! Should I get the morning after pill?

Me and my boyfriend had a lot of unprotected on the 26th. He tried not to c** but I'm sure he pre-c**. I am also on Yasmin birth control which I stopped taking on the 28th because my pack is over. I've been useing Yasmin for about 5 months now, so i'm not new to it. I should be getting my period now but I haven't got anything yet. Today is the last day I can take the morning after pill.. should I buy it or should I just keep waiting? I also have two pregnancy tests and I don't know "when" to use them. Thanks for the advice! I'm really stressing out.