So January 27th I had an appointment with a doctor and got treated for Chlamydia and a Uti, my boyfriend was treated the same day. And before anyone says one of us was cheating neither of us were he got it from a girl he slept with before he started dating me and didn't know. We'll anyway I took the medications like I had to and was told that the antibiotics wouldn't cancel out my birth control pill, but we used a back up method anyway. Well another <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> I have says I'm 18 days late. I haven't taken a test just yet mainly because I'm nervous about the outcome. This has happened before where I ended up being almost 20 days late and got my period. Could this be another one of those times or could this he antibiotics have canceled out my birth control and I could be pregnant?!