My First Day Of My Last Period Was March 16.

My first day of my last period was March 16. I slept with someone on March 27 at 9:30 am. I took the plan bill pill the next day at 1 pm. On April 2 I had unprotected sex with a different partner. I took a clear blue pregnancy test this Thursday which came back positive and said I am 2-3 weeks pregnant. Is it possible that the pregnancy was conceived by partner #1? Considering the results of the test, when ovulation occurred and the effectiveness of plan b after 27.5 hours.