What Causes Headache With Neck Pain?

hi i am 3 months baby.. i have started headache since a month now..it starts from back side with neck pain first always on right side...its mild to moderate .sometimes feelimg some imbalance as welll.doc in india referred me stemtil feels better with it. but how much can i continue sice i am breastfeeding...what can be the reason behind this...when i think it becomes more stressful and stress triggers the main more..