Took Plan B After Intercourse, Have Menstrual Cycle Differences. Any Pregnancy Chances?

I dont remember the day of this month that i had intercourse with my boyfriend but i do remember buying and taking the plan b pill the next day. Although, me and my boyfriend were not sure if he ejaculated or not, so we decided to buy the plan b just in case. I am currently waiting for my next menstrual cycle and i am worried that i may be pregnant because even without intercourse, i do have some menstrual cycle differences. I dont usually get my period within a week like most women. I get mine around a month or two. So im wondering, is there any chances i may be pregnant due to any menstrual difficulties?