Did Plan B fail ?

End of last month, condom broke and he came inside of me. I took plan b 3 hours after. I never felt sick. When my period was scheduled ( suppose to come a week after incident ) it came a day late according to the app. Lasted it's normal time, a little heavier. But now, 20 days after the incident I'm feeling sick, I'm having like ovary pains, and feeling nauseous and I have been tired lately. My period is due in 12 days because I haven't had it in this month. Idk of I'm nauseous because I'm lactose intolerant and I had sonic 2 days in a row( bad I know ☹😩) or if I'm pregnant. I've taken plan b before and one similar effect is getting sick after watching fast motion films. I'm so scared. Any thoughts.