Okay,I have been on birth control for 4 years now. My last menstral cycle started on July 3, 2013, then I started by birth control like normal on July 7, 2013. But my doctor put me on antibiotics which I took July 9-16, and when I googled the type of antibiotic it said it could make my birth control ineffective. Birth control is the only thing I use for protection against pregnancy. I am supposed to start my cycle again on July, 29 but I started spotting kind of brown blood on July 20th, it has been off and on all week, 20th - 26th, but it is kind of a pink color now, I can wear a tampon for well over 24 hours and not have one in at night, I am not sure what this means and I need help, I read that it could be implantation bleding, so could I be pregnant?? I need help