Irregular periods?

Hey ladies :) so for about 8 months now my periods have been between 28-32 days. Would you call this irregular, and would there be anything I can do to regulate it? Before, my periods were every 28 days almost down to the hour! Then one month I was 2 days late and didn't know why. The next month was back to 28, and the month after was 32 days! I'm 18, practice safe sex and not pregnant, healthy weight and I eat a balanced diet. Is there any reason why it could be so irregular?