You generally need to either be having consistent contractions close enough or have your water broken. I was 2 cm with consistent contractions 3 minutes apart and I was in triage until I was dilated to a 5. Then they finally admitted me.
My doctor usually takes them in at 3 cm but some other doctors at the hospital I'm delivering at waits until 5 cm and no your water doesn't have to break. Some people start having contractions before there water even breaks. Or your water can break and you still won't have contractions. it just depends on your body. The nurse at the hospital told me that when I asked.
It can be either of those things. If you're contracting 3-5 mins apart then you should go. They'll check to see how dilated you are and if you're at least 3cm they'll monitor you for an hour 👍🏻