What Causes Abdominal Pain And Spotting?

Due the day of my period, I had a ten minute bleed. I have been having little spottings if blood every now and then. Its been over two weeks since my period was supposed to of been due. I had tested negative over a week ago. I have experienced sore and colour change in my nipples and sickness and tiredness. Recently I have been getting abdominal pain, left side, may be my ovary? Will be at the doctors soon, but can you help?