umm what??

So I'm currently on June 1/20 birth control. It's a continuous pill where I don't have periods. HOWEVER due to a billion different illnesses hitting me back to back to back, I've been on steroids and antibiotics for the past month and a half. My SO and I are sexually active, and because of my birth control(yes, we weighed all our options)we use the pull out method and as most of you ladies know it's not always effective for a multitude of reasons. So my problem is this morning when I went to the bathroom, I had dark red blood in my panties.. Why? Seriously why? I haven't had blood come out of my vagina in months, almost a year. Why am I bleeding?? I'm probably being stupid and freaking for no reason but I don't understand.