Late period

I had my period mid October, had sex, then took plan B and got my period again 2 days after that. I haven’t had my period since, also I haven’t had sex since that time in October when I took plan b. It is now day 49 of my cycle. I tested twice on December 7th it was negative, tested again December 16th and it came negative again. Could this be plan b messing with my period? Should I test again? Or when should I be having my period again?