I have heard that this can be caused by many things. I don't know if you have a lot of stress but I would try maybe evaluating that and also diet. There are a lot of things that say that nicotine, caffeine, etc. can cause your periods to be irregular. Did you recently start or stop any form of birth control? If it is none of these issues than it may be fibriods or endometriosis...all of which you would have to go to the doctor and have checked. All of these are things that you may want to take a look at. hope this helps.