Ever since I was a teenager my cycle has been exactly 28 days. It's always arrived on time and lasted 5 days. The past 4 months it's been 3 days late and I have no clue why! (I'm 25 now) Nothing's changed in my life/diet. I'm currently a day late now and have no symptoms (I have endometriosis so symptoms are always there usually!) help! Anyone had a change like this and know why?