Contractions or BH?

This is my second pregnancy & I can't tell if I'm having contractions of BH. My stomach has been tightening up more than 6 times in the hour & it feels like a dull period cramp. My back muscles have also felt really sore as if I'm stretching too far. With my first baby, I had contractions but never felt them. What should I do? I'm almost 32 weeks