Always when im go to sleep i have a headache at the right back side i can't sleep because of it what could be it?

Headaches: End of day headaches are most likely 'tension type' sounds like a chicken/egg type of problem since poor sleep causing tight head and neck muscles and headaches and your headaches are keeping you up. I would work on your sleep hygiene - wake up same time, go to be same time, no naps, limit coffee and alcohol, power of your tv and computer for 1 hour before bedtime, and exercise more.

Irritation?: Perhaps you have an inflamed nerve or muscle at the base of your skull and when you lay down it is aggravated. Take ibuprofen before sleep and consider seeing a chiropractor for treatment.