I broke my leg at the beginning of this month at the end of my period, recently my incision from my surgery became infected and I was put on bactrim DS. I have taken tri-Lo sprinter for 2 years now. I completely forgot that antibiotics effect birth control and had sex on Wednesday of last week. Also last week, Tuesday-Saturday I had spotting. But it was heavier than what I have read about and a bright red color like my normal period. I did not begin taking my antibiotics until Thursday night. Yesterday, Monday, I realized that antibiotics and bc pills interact so I took a Plan B even because certain websites said that it COULD work up to 5 days and I thought it was worth a shot. My question is, do you think I'm pregnant? Or is the bleeding just from stress? And do u think taking plan B helped?