Took plan b right after period ended, three days later another period started. im worried this pill messed up my body since ive had two periods?

No worries: Plan B can alter the menstrual bleeding for the cycle in which Plan B was taken, and sometimes the next cycle too. One's menstrual pattern should return to "usual" after that. Also, be sure to check a home pregnancy test about 3 weeks after sex, because Plan B works most of the time, but not all the time. One should put in place a good Plan A, so that Plan B will not be needed again.