Thanks for your question. There are many different possible explanations, so it is important to speak with your doctor
about your concern. Changes in your diet, your exercise, your birth control
, your overall health, and many different things can have this result. Of course, there are other things that could be even more concerning, and so you should discuss this with your doctor. The final explanation will also likely have something to do with your overall age and weight, since either of these can explain what is happening. For example, women who are overweight will have dysregulation of their menstrual cycle that can impair the ability to get pregnant and will also make their menstrual cycle come at unpredictable times. This can be a sign of overall poor health as well, and is not something that should be disregarded. Again, please speak with your doctor about this question so that you can get the help that you need and determine if there is something more serious that is causing these symptoms that you are describing. He or she will be able to help you understand and correct what needs to be corrected, potentially with some additional testing.