You don't include any details, such as your age, which would be very helpful when trying to answer this type of question.
If you are a young teenage girl, it is common for this age group to have irregular periods. However, if you have had sex at all during this time, I would scoot myself down to the dollar store for a pregnancy test just to check.
If you are in your 40's or 50's, this could be signalling menopause. So again, when you submit a question, a few details would be very helpful. Hope this helps.