Hello, thanks for writing in. As you have not provided complete details of your heart attack and its treatment, we are going only by what you have said. The neck pain due to wrong sleeping posture will be more of musclular pain in nature and increased by movements. The cardiac pain is generally stabbing in nature and doesnt have any relation to pain. Please consult your cardiologist if in dilemma to rule out cardiac cause of pain. Then perhaps you could take constation from an orthopedic surgeon as required. Hope this helps.