Early labor? Attempting VBAC & currently 36w4d

My original due date was 7/30 which would make me 36w4d. going off of my 20 week ultrasound it looks like they bumped my due date to 7/27, so that would make me 37 weeks. I have been measuring 2 weeks ahead for the past month and just had an ultrasound done a couple days ago. I don't know what true labor feels like because I never went into labor with my son even after being induced I didn't experience contractions. This baby is super low, I feel has dropped alot in just a couple days and I can barely sleep. I have horrible back pain and cramping on and off. like I said I don't know if I'm having contractions but should I contact my doctor?

Picture - left is this am and right is just 2 days ago... what do you think?