I have been taking Tri-Sprintec for about 2 years now. My doctor prescribed Nitrofur-Macr 100mg for me in late Dec to keep off UTI infections. I only take as needed. My last period was March 23, and I have taken 9 Nitrofur-Macr since then. I have had intercouse 4 times. The first 3 times he pulled out prior to ejaculation and the last time on April 17 he didn't so I took Next Choice within 24hrs. The 2nd pill being taken at 7am Mon. My period should have started the following Wed or Thur but has not. Is it normal that the Next Choice could affect it starting or is it very likely that I could be pregnant?