Pregnant?

So last Friday I took my pill at 9am as usual and all was good. My boyfriend and I woke up at 11 the next day (Saturday) and ended up having sex, we used the pull out method as half way through I realised I hadn't taken the pill that morning. Today (Monday) I've had light spotting and have been feeling extra tired and slightly nauseous. Apparently these are the earliest signs of pregnancy? I've spoken to my boyfriend about it and he seems confident we aren't pregnant but I can't help but wonder. Can anyone help or has had the same experience?