I am experiencing headache for several hrs on the back side of the head every time after semen discharge.it gets better by eating at least 2 meals.

Postcoital headache?: Is a possible explanation see below for general advice http://www.migrainesurvival.com/orgasmic-headaches For specifics as per the information sheet it is important to see a doctor licensed in your area to rule out other causes for your headache including some that may be serious, and to look at treatment options for you.

Not uncommon : Ejaculatory headaches are not uncommon. If you do not have hypertension--and you should be checked for this on several occasions--then a prophylactic medication can really help prevent these. If there is a family history of Berry aneurysms, you need to see your family doctor.