Labor won’t progress

So I am 37 weeks and 5 days. I know I have a couple weeks left but I have been with menstrual like cramps and irregular contractions for about 5 days now. I’ve lost multiple pieces of my mucus plug and I thought my water had broken. Went to the ER and my water had not broken I was 3 1/2 cm dilated and 75% effaced, my contractions were about every 10, 15, 4, and 3 minutes apart but only last at an average of 40 seconds. They are also not very painful so they sent me home until my labor is actually happening. I just am confused as to what’s happening and wondering how long this will all last. Any women experience something similar?