What Causes Tight Feeling In Stomach, Abdominal Pain And Sore Breasts?

Hi, I am having pregnancy symptoms but I am not sure if I am pregnant or just being paranoid. My stomach is tightening and sending pains all across my abdominal and my breasts are sore. I had my period but it was lighter than usual and only lasted three days. I have read and it said that spotting was normal but mine looked just like period blood. It was not pink. Can you give me any advice? Thank you!