35 weeks dilated

I went to L&D Monday because I’ve been having a constant menstrual type cramp in my back - I wasn’t dilated or anything so they sent me home and just said to drink more water. Last night i ended up going back because the cramping was getting worse and the pressure became unbearable. I’m now 2cm dilated. Is that normal to jump from nothing to 2 in 5 days?! Could this mean baby is near?? STM but with my first my water broke at 39 weeks - I never had this. I woke up this morning with the same type cramps. I’m afraid I won’t know when to go back lol