warning tmi picture

hey guys I'm 33 weeks pragnant was having pretty intense contractions yesterday and some on and off today irregular well I took a shower and all. We'll now I had this come out of me when I wiped. what is it?? is this my mucus plug or what. I've been admitted 3 times for preterm labor and I'm dilated to 1??? please help? what is the little black line stuff?