Braxton hicks or the real deal!?!

So I'm 38w5d today and last night I started having some annoying back pain. It turned into period like cramps throughout the night. Painful but nothing major. All morning I've been having what feel like contractions but I'm not sure how to tell. I'm a FTM...I've been trying to track them and there is some consistency. I lost my mucus plug a week and a half ago and was dilated 3cm last Monday at my appointment. I have an appointment tomorrow morning so I'm hoping to get some insight. Any thoughts?