weird discharge after sex

Julia
Hey! 
So my gf and I had a lot of sex this weekend. Fingering and oral. All very enjoyable and not painful. I should add that I've only had sex a few times prior and not this intensely before.
I am not pregnant. There has never been a penis anywhere near me. 
My period is about a week away and I'm noticing some light brownish mucus-like discharge which I've never seen before. It doesn't hurt and nothing else is off. 
Has this happened to anyone else? Especially those who have sex with fingers and tongues primarily? 
Any idea what it is or if it's a problem? Thanks.