lots of ideas but unfortunately ideas are not patient-specific diagnoses. you will have to make an appointment with your gynecologist or primary care medical provider to see what is going on. the complexity of this problem cannot be adequately addressed over the internet based solely on your brief description. you need to be examined and have a few diagnostic lab tests.
last period was light this month am 7 days late but not had sex this month. last month period was light and bright red before started had nagging pain in left side near ovary. thought may been pregnant as been trying. five days had brown discharge for few days then stopped. now i am seven days late and usually regular but not had sex this month. having cramps as if coming on but nothing just some light watery discharge. any idea what can be?