Took Plan B; Symptoms of pregnancy??

I had my period for 7 days (usual for me) then 2 days after had unprotected sex and took plan b! 6 days later I got another period for 4 days! I’ve been off my period for 3 days now and I threw up this morning and feeling week all day. There is no way I’m pregnant right? Periods=Not pregnant?? So the plan b did work right???