Braxton Hicks or real contractions?

I’ll be 35 weeks as of this Friday. I’ve had like one Braxton hick contraction before today and it only happened once and it was a few weeks ago. Well today I was at work and they started at 7am and it’s been 13 hours and it hasn’t stopped. My moms a nurse and she asked her friend in labor and delivery and she said I was fine. But has anybody else had this happen and it been real contractions? They’ve been about 10-20 minutes apart and it’s uncomfortable and I feel crampy (like a really heavy periods about to start or something) and it feels like I’m having a lot of pressure. My job consists of my walking at a brisk pace 8-10 hours a day. I’ve been worried we won’t make it to our due date anyways although I haven’t had any problems so far except today.

What’s been your experience with Braxton Hicks? If you’ve ever dealt with pre-term labor what were your experiences with that and how did you know to go to the hospital?