Contractions!

How do I know when to go into L&D? I’m 37+5, scheduled for my third csection in 4 days. I’m having really uncomfortable contractions now for the last 3 hours or so, I haven’t timed how long they are or how close but I can tell they’re pretty frequent. My belly is getting very hard and I’m having a ton of pressure/stabbing pain in my vagina. The contractions aren’t painful yet, just super uncomfortable to the point where I have to stop what I’m doing and breathe through it. What do I do?!