Obviously a FTM here, but wondering from those of you who have been through this before how you tell the difference between normal end of pregnancy back pain vs the beginning stages of back labor?

I’m 35w6d and my back has been KILLING me this morning, like my typical period backache/pain but x100 worse. I’ve tried lying down, stretching, drinking water, and currently in the tub but nothing really seems to relieve the horrible ache. Not sure if this is just normal lower back pain from being super pregnant or the start of something. I’m probably just being anxious because hubby just left for a work conference this morning and I’m afraid I’ll go into labor and he’ll miss it 🤦🏻‍♀️ so any words of encouragement or stories of previous experiences are welcome 😊