BH or the real thing?

I'm at FTM due in 2 days, at my appt on monday I wasn't dilated and I wasn't effaced at all. Sense yesterday I've been having a dull ache in my lower back an goes around to my sides then goes away. Late last night, around 3am I woke up with heavy period like cramps, and my lower back still had the dull ache. It kept waking me up about every 45min-hour. I don't know if its BH or the start of real contractions. It feels like she's sitting in my butt, literally.