Hi, am having back of the head headache left side, even neck pain,from past 7-8 years,I don t what type of head ache it is, 5 years before dr prescribed Naxdom 500 mg, earlier it was good, means if I take one tablet it works for a month, now every 2-3 days am getting head ache, am taking naxdom 500 mg from past 5 years, for every 2-3 days, is it safe? What can I do to get rid of this headache,