If you have a period for one day and spotting two days later wit lower back pain what do this mean?

Need more info: It is hard to say what that means without more details about your bleeding. Is this a normal or abnormal pattern for you? Changes in periods, especially with less bleeding or spotting can mean pregnancy, and any pain with abnormal bleeding might be a problem. Or might not. If you have more trouble or additional symptoms, please see someone to get a better answer.