Took Plan B 12 hours after sex, spotting a week later for 2 days, then headache and period came on the 3rd day. Can I still be pregnant? I'm 180pounds

Maybe not, but... Plan B can alter the menstrual bleeding for the cycle in which Plan B was taken, and sometimes the next cycle too. One should 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.