It could be POTS. that's what it sounds like as LindaTx says....normally dr's go by 10/20/10 rule - your bp can go up or down by 10/20 (120/80) and HR by 10 but some dr's won't dx pots unless it's a 30 pt increase or more and some of us ANS (autnomic nervous system) patients won't get a dx and help even with that increase :(
some dr's just don't understand ans dyfunction or dysatuonomia - here's our forum for ans issues:
http://www.medhelp.org/forums/Dysautonomia-Autonomic-Dysfunction/show/266
here's some info on ANS; maybe you have other symptoms also?
http://www.medhelp.org/health_pages/Neurological-Disorders/Autonomic-Dysfunction-FAQ/show/181?cid=196
when I'm back on my pc I'll send you a link to take your bp/hr according to Vanderbilt; I think it's after 10 minutes of rest, then you take your bp/hr on a monitor at 1,3,5, 10 minutes then standing 1,3,5,10 min but I can't remember exactly.
Here's a list of doctors and clinics who specialize in Dysautnomia and ANS issues like POTS
http://www.medhelp.org/health_pages/Neurological-Disorders/Dysautonomia-Specialists/show/717?cid=196