Do antibiotics cancel your depo provea birth control shot?

I was taking antibiotics for a tooth infection and I'm on depo provera. Does the antibiotics cancel my birth control? I was on the antibiotics for maybe a month or two and I had unprotected sex .. Is it possible that I could be pregnant? I'm only 17, and I don't know what to do. I'm in a very serious relationship with my boyfriend who is my soon-to-be fiance. We don't want kids yet and I'm really freaking out on this because I think I'm pregnant. I had sex in november, I'm on my second depo shot and I'm still taking antibiotics. I'm also taking lexapro for depression and anxiety. So I'm really curios if I could be pregnant. The last time I had sex was november 8th. In october, I had sex while on my 2 week period because of depo provera I had a very long period. I had sex on my period 3 or 4 times the day before and after my period stopped. Can someone please tell me what I should do. I don't know whe my period will start cause I'm on depo and usually I start the 6th of every month. Yesterday december 2nd, I was spotting for a very few hours, it was light pink and brown. Now I just have brown spotting. So please help me out. Thank you.