I had that last month. I had diarrhea for over a week only in the morning with clear mucus in it and my breast were so sore I couldnt' take a shower, I had to take a bath. The water pressure hurt sooo bad and I had to leave my bra on all day. I was convinced that I was pregnant, but I ended up not being. I had a terrible period afterwards. I still wonder every now and then if I miscarried.
I thought the diarrhea with mucus and sore breast were pregnancy signs, but apparently they may be a result of prenatal vitamins. That's what i'm guessing.