BIRTH CONTROL EFFECTIVENESS WITH VOMITING

Q: I am on birth control pills, but I have had unexplained diarrhea for almost a month. I went in to see the doctor to check for parasites in the stool, but did not ask about the effectiveness of the pill. I read on the Yasmin Lotus information label that diarrhea and vommiting can lower its effectiveness. I had sex using only the birth control as protection earlier today (no condoms)...Is emergency contraception necessary?