Braxton Hicks?

This is my 3rd baby (due sept 17) and I've been having what I think are BH contractions. I had the same thing towards the end with my other 2 pregnancies but any OB I've ever described it to seemed confused so I'm wondering if anyone else has ever experienced it. Basically my stomach gets tight but I also get short of breath and feel like there's a weight in my lungs? Like a really tight hug kind of. OB said BH but not sure why I'm short of breath each time.