What Causes Dizzy Spells While Holding Head Down?

I have been having dizzy spells when I hold my head down, slight headache all day long plus I can't move my head to fast I get dizzy. I am 33 years ,my weight is about150 I have been lost alot of weight not trying to,my hight is 5'5 an a half .Both of my parents had high blood pressure. I check my BP it read 133/87 .this has been going on for a week now.what do this mean an what should I do?