anyone with the same experience ?

Ok so I started spotting a week before af expected arrival but it's not enough to wear a pad/tampon but enough for a panty liner. It's been going on for 4 days today & af isn't due until the 18th. Now, I was taking oral medication to treat bacterial vaginosis for a week prior to spotting so could that have affected my cycle ? I have a normal cycle & I've never experienced an early period before. Also I'm not trying to conceive but I'm also not preventing it.