Brown vaginal discharge?

Starting yesterday, I've been finding a lot of brown blood discharge in my underwear. Usually that happens just a day before my period but my period comes around the 14th or 15th. I'm really concerned because I just woke up to a puddle in my underwear and I have cramps as well. (I've never had this happen to me before and I've had my period for 7 years)
I read online that it could be pregnancy but my boyfriend and I use a condom each time we have sex so I'm trying to rule that possibility out.
Does anyone know what could be the cause of this?