How do you distinguish difference between late period & early miscarriage blood? & pain?

Miscarriages are common with first pregnancies, and are difficult to separate from a "late period" unless one gets a serum HCG test to detect low levels of pregnancy hormone. Your menstrual history can provide information about "pain and bleeding", and if this instance is typical of your normal cycle's symptoms, without a test it is not possible to prove the cause.