What are these pains? Braxton Hicks?

I'm 38 weeks and 2 days pregnant, although at the hospital today I had a growth scan and the baby is actually the size a baby would be at around 40 weeks and 5 days and his current estimated weight is around 8 pounds... His head is engaged and is laying spine to belly. For the past few weeks I've had period like cramps on/off and the occasional twinge and back ache but since last night I have had constant back ache. Its in my lower back and round my hips. The only way I can describe it is imagine having a bruise all the way around your back and belly and someone squeezing it. I get the odd bad twinge that takes me a back but the back pain is permanently there aswell as having really bad pain down below... I'm feeling a lot heavier and its hurting so much to walk or even turn over in bed. I'm not getting much sleep lately with the pains. I've tried walking off the back ache and pains and changing positions but nothing seems to be working. Are these all signs of Braxton Hicks?? This is my first pregnancy and even though I'm aware these are all normal pregnancy symptoms, I'm just not sure as whats causing them and what they are... Anyone else have any clue? xx