38 weeks 5 days

I'm 38w5d today, FTM. I'm having extreme pelvic pressure (my public bone feels like it's going to split in half). I was checked by my OB on Monday and I'm already 4cm dilated. The pain only occurs when I move (walk, turn, sit, stand--when I lay down it feels ok). I don't think I'm having any contractions because they aren't painful, my stomach feels tighter at times though. I'm not sure what to really say/explain if I were to call the clinic line..Has anyone had this happen and it be a sign of labor? What did/would you do in this situation? I'm just freaked out since I was already at 4cm on Monday and don't want to wait too long till I get to the hospital if this could possibly be labor.