Going to your gynecologist or an endocrinologist would be advisable. If you have hormonal issues, the doctors will probably put you on birth control to help you ovulate and get your period started. You should also have an ultrasound done in case there are structual abnormalities like cysts that can cause your cycle to be irregular.
I think if you call your local planned parenthood they have this thing called the morning after pill, which if im not mistaken jump starts your period after a night of unprotected sex in hope of preventing pregnancy.
I had this problem not too long ago because I am in a perimenopausal time in my life. I seeked advice from friends who are into natural herbs and remedies. I took a supplement called Colostrum, and within three days my period started. Colostrum also has other health benefits.
What I do is eat more, but if you don't have a normal or fast metabolism, this might not be the best thing for you. I just know that when I eat a few big meals around the time my period is supposed to start, it comes sooner.