Constipation vs. Contractions?

I haven’t been able to “go” for about a week now. Just started barely going this morning. I went in for my NST today and had some contractions but they stopped after having some water.

Fast forward to now: I’ve had 4 cramps that feel like gas pains/cramping within 40 minutes. A few of those were while I was on the phone with my mom. She wants me to call my OB and get checked again.

What’s a good way to tell the difference between the two? Or should I call in?