Can you go into labor without feeling contractions?

Last week I was 1.5 cm dilated and 80% effaced. As of today I'm 3 cm and completely effaced and they can feel his head and I've also lost mucus plug. My doctor seemed surprised that I haven't felt any contractions and feel labor could start at any moment at this point. Has anyone given birth and not had any cramping or significant or noticeable contractions?