Doctors can you tell me why do i have a sore neck and a constant headache?

Muscle spasm: 30's person with neck pain and headache likely has cervical muscle spasm causing a muscle tension headache. Chronic head tilting or improper posture while sleeping might have aroused. I assume is more chronic than acute. If acute, severe, and with fever and sense of illness then an emergent evaluation for spinal infection is in order.