Weird period or implantation bleeding?

I had unprotected sex on September 15th and within 15 hours I took the plan b pill. About 6 days later I got a brown discharge, the next day I had my normal period, but on the third day just some spotting. This spotting lasted about 2 days.

I took another plan B about 2 months ago.

Was this my period? should I worry about being pregnant?