Braxton Hicks?

Brittany • FTM, impatiently waiting on a baby girl!
I am 31(+5) weeks. I have been have a back pain (spasm?) that lasts about a minute and is so intense and strong I can't talk through it and it takes my breath away. They happen irregularly so I didn't think they were normal contractions, plus I have no stomach cramping. 
I informed my midwife and she said, Braxton Hicks don't cause pain, but she didn't know what it was.
But most other mommas say BH do hurt! 
What do you guys think? Should I be nervous?