FTM! When did you go into labor??

When did you guys go into labor with your first baby? I’ve been having lots of pressure down below with back pain and the occasional lightning crotch. Baby was measuring almost 2 weeks ahead at his 29 week ultrasound. I just want to know when i could realistically go into labor so I can be prepared. I’m 31w 3d. I have an appointment on Tuesday but I’m just not sure how to explain it but I have this gut feeling I won’t be making it to my due date month (1/17/20) let alone the actual date.