I THINK IM PREGNANT ?!! Help !!!!!?

Well I turn 16 this October but I've been sexually active for almost 2 yrs. Well 2 Thursdays ago I had unprotected sex with this guy. I was suppose to have my period on the 25th of June and that didn't happen! The latest I would have gotten it was the 28th and it still hasn't came ! Plz help !!!