Odd bleeding

Sorry if this is a little tmi, but for the last week I've had a feeling my period is coming, so I have been using tampons. However only the tip of the tampon has had brown blood on it. It's like a very small amount, I wouldn't even consider it a period. But it's weird that for like a week the blood has been so minimal and only is found if I wear a tampon. (Like it doesn't leak out or anything). I'm on birth control since 5 weeks ago. Could this be the reason?