headaches when laying down

hi , i have a headache when i lay down  which is making sleep a problem , my blood pressure is fine i am wondering what else it could be..

[hava]

Drink half glass of warm water, before you lie down. Then do this pranayam for 20 minutes, with your eyes closed. After doing this for five days, let me know how you feel.
Build up your timing gradually.If you feel tired or dizzy, stop and resume after one minute.
Anulom Vilom pranayam –
Close your right nostril with thumb and deep breath-in through left nostril  
then – close left nostril with two fingers and breath-out through right nostril  
then -keeping the left nostril closed  deep breath-in through right nostril
then - close your right nostril with thumb and breath-out through left nostril.
This is one cycle of anulom vilom.
Repeat this cycle for 15 to 30  minutes twice a day.
Children under 15 years – do 5 to 10 minutes twice a day.
You can do this before breakfast/lunch/dinner or before bedtime or in bed.Remember to take deep long breaths into the lungs.You can do this while sitting on floor or chair or lying in bed.
September 27, 2011