I agree, any kind of discharge you should let your doc know about, most of the time it will be nothing, specially if it is after you having sex or anything that might have bumped your cervix, because it is more sensitive then normal now that you are pg. Brown discharge and darker is old blood, so it could be something you did a few days ago and it is just now coming out. good luck, I would not worry though. I had it lots in the beginning of this pg.