What Causes Delay In Periods Without Having Intercourse?

So I m kind of concerned about something. So I m an 18 year old girl who started her period when she was about 12 or 13. Well, my period this month is almost a week late. I ve never had sex before, but I have made out with my boyfriend a little hard core sometimes. But we ve never actually had sex or even taken clothes off. After we have these little sessions, I almost always have discharge or a little wet in the down region. Is there a reason my period could be late? And what s happening with the whole discharge thing?