Help!?

Okay so I’ve heard having diarrhea in late pregnancy can be a sign of labor, I’m currently 33 weeks pregnant and I was just constipated like 20-30 minutes ago!! I now have terrible diarrhea! I’ve been having alot of pressure/pelvic pain today and was contracting on and off the whole time I was grocery shopping which was about 2 hours long. Has anyone had any similar experiences? The only time I’ve ever had diarrhea in my whole life was if I’d taken laxatives ☹️