Cramping at 17 weeks

Jay
For the past couple of weeks I've had period like cramps very low, and they're a little more intense than period cramps. I asked my doctor at my appointment last week, and he said it's nothing related to my cervix or my uterus because my sonogram looked great. He suggested gas maybe. Sometimes they're so intense, I feel them in my back. No bleeding though. Anyone else experiencing this?