Aftr 3 days of mised period, i had a blood test 4 pregnant and it came negative.stil i can't believ.what could b the cause 4 my abdominal pain + misd period?

Many things: Many things from pregnancy in the fallopian tube to cramping from an impending period. If no period in one week recheck the pregnancy test and/or see a md immediately if the pain persists as your body is sending you a email(pain).

Pain: You may have an ovarian cyst which forms after ovulation. It can be quite painful. Most of time these spontaneously resolve, but the pain can be quite severe. See your doctor if it doesn't resolve in a couple days or if it gets alot worse.