37+1 with a question

I have a call into the nurse line at my dr's office...I have noticed my discharge is slightly darker today and also I just smelled it and it smells like vinegar. (Gross) Any ideas if that's fluid...I've been experiencing some BH contractions but thought possibly that I was having actual contractions last night because my back was killing me as well. Any insight would help because this is my first pregnancy. Thanks!