Take plan b may 6 got my period after a few days and after 3days im bleeding again for 3days am i pregnant?now i have bad cramps and lower back pain

Very unlikely: It is virtually impossible if you have you period. You can always do a home pregnancy test.

It may be side: effect from Plan B. Potential side effects w emergency contraception include: menstrual flow changes (spotting, bleeding, early or late period), nausea, vomiting, dizziness, fatigue, headache, breast tenderness & abdominal pain or cramps. Take pregnancy test & notify dr if your period is 7 or > days late.