What is wrong with my periods?

Hi i had a normal 28 day cycle blood loss was 3 to 5 days medium flow, for the past 6 months i've just had spotting dark brown no blood 23 days cycle what could be causing this? and also i'm getting all the period symptoms just not the blood loss like i would normally doctor did blood tests ok i was seriously unwell 2009 also alot of stress bereavement but can't understand why my body is not giving me a normal period now?