What can a prolong headache fr about 15days indicate to? Medicine gives relief fr only an hour! Also have nausea.

Related or not? There are lots of possibilities here, all of which can be addressed by a physical exam and appropriate testing. Migraines for example can affect both head and gut ("intestinal migraine"). Please however don't contribute to your stomach upset by taking excessive nsaid's aimed at alleviating head ache. Get checked to rule out more esoteric pathology.