Hi. My Last Period Was On March 4 And We

Hi. My last period was on March 4 and we were fooling around on April 5 (i did not have my period yet that time) He inserted his penis without for like 2 seconds it was very quick. But I have been very nervous about the probability of getting pregnant because of precum so i took plan b 31 hours later. It has been a week and I have no period yet. I only have this yellow discharge in my underwear. Could I be pregnant? Please answer.