Hi I'm Currently Late On My Menstrual Cycle By 9

Hi I'm currently late on my menstrual cycle by 9 days I tested with a hpt on the 4 day and 8 day and both were negative!I do have a 7 year old child and I was recently pregnant 7 months ago but experience a miscarriage 9 weeks into my pregnancy about a month later I was back to my normal menstrual cycle which is 31-33 day cycle.What could be wrong with me if I'm testing negative?