Hi, I Have Been Experiencing Abdominal Cramps And Lower Back

Hi, I have been experiencing abdominal cramps and lower back pain since ovulation. Had sore boobs and constipation also. My periods was due yesterday and I usually have regular periods with 28 day cycle. Today morning got dark brown discharge in very small amount. Later the amount increased but the flow is light. Usually I get heavy flow on first day itself. I have slight abdominal cramps too. Is there any chance of pregnancy or should I give up that hope?