Alyc

At first I though I just got up too quickly but then I realized that wasn't it. When this started to happen it was just one or two times a week, now it's getting to be four or five times a day. I'll be sitting down and about two or three minutes after I get up, I have to stop and fight against the blackness threatining to close in on me. I become very dizzy also. I've started to get dizzy just sitting or lying down and today I just moved my upper body a fraction of an inch and had to fight to keep from passing out. Now I get headaches every time I stand up and I'm wondering if anybody has any suggestions as to what could be the matter with me. Oh, and I've checked my blood pressure and it's perfectally normal, so that's not the problem. Any ideas?