Don't know if you can help me...?

I really don't want to sound immature like all the other teenagers on this website. But recently, i would say about 1 month and a half ago I was fingered by my boyfriend for the first time. I am 16 and this is the first sexual experience I had had and I was sure I was ready. I had my period a week after this happened but when it has come to this months (due on the 24th July), I still haven't come on. I am now 7 days late.. and I'm wondering as it is near impossible I am pregnant obviously (as i had a period after), if there is any other reason my period is this late? For a year or more now, it has been very regular, so I have found it weird.. that I am suddenly late. Many thanks!