periods can become irregular if your stressed out are you? if so relax and dont worry about it or you could stop it appearing altogether. other reasons can be meds you take, contraception your on eating disorders. see what happens with your next cycle and if its the same you can always see your doctor. good luck god bless.
Did you test for pregnancy .In early pregnancy bleeding/spotting is common and it comes around the same time when u are expectiong ur period.