So every month I usually start my period around the 23-25. Since June of last year I've never started any later. Well today is the 28th and no period. Glow says I'm suppose to start Thursday the 31st. That would mean my normal 28-29 day cycle just changed this month to 36 day cycle! I've tested and the hpt test are very very faint or negative. Any idea or opinions? Has this happened to anyone?