Your profile says you're a male.
If you're concerned, see a doctor. Could be many issues including endometriosis, PCOS, and other causes for concern.
You should definitely talk to your doctor about this, it could be something that is easily regulated or something that requires medical attention (though I am hoping not!).... are you trying to get pregnant? If not, you should talk to your doctor about the different kinds of birth control pills and how they may help you regulate your cycles. If you are trying to get pregnant it's important that you take care of this issue first. Many times women have a serious medical condition that affects their fertility and can become worse if untreated. Make an appointment soon and see what your doc says.
you should go to the doctor ;) it could be many things