A 28-year-old primigravida at 39 weeks gestation presents to the labor ward with regular uterine contractions every 3–4 minutes. On examination, the cervix is 3 cm dilated, 80% effaced, and the fetal head is at −2 station. The patient reports pain in the lower abdomen and back. Vital signs are stable, and the fetal heart rate is 140 bpm with normal variability. What stage of labor is this patient currently in?