Light brown discharge after clitoral masturbation?

I am 19 and a virgin and so is my boyfriend. We do touch each other sometimes but there has never been penetration. We fooled around a few weeks ago and this morning we were fooling around and after I went to the bathroom I noticed a light brown discharge when I wiped. It is six days before my next period. This discharge is similar to what I experience the day I start my period but it is a much lighter flow. I am also on birth control to regulate my period so I am always on schedule. What could this be? I have never experienced this and I am just being overly paranoid.