no it's normal... well i dunno about falling but i feel that way alot of times, like if i've been sitting there for awhile, and i stand up fast, or stretch to hard i come about 1/2 a second from passing out before it goes away.. i'm pretty sure everyone experiences lightheadedness once in awhile (even severe cases of it) it's when you're cutting off the blood flow (which also is the oxygen supply) to your brain that it is harmful, well to a major extent, i'm not sure if that lightheadedness could cause any damage, if it happens often, then you might have a problem, i usually experience it from once or so a week to once every two weeks.. if you experience it too much more frequent, you might wanna talk to a doctor, but it's nothing to really worry about (something to worry about, well an example you're sitting there then you just start coughing up blood like crazy, then you'd wanna worry. as for your doctor... well i've seen a great decrease in doctor effective-ness for the past few years now.... seems like when this big boom of people entering medical fields (i mean we do need them and all...) it seems like they do anything to get you in and out as fast as possible... which means not a very thorough check up, or doctor-patient communication....... which as you could guess, could lead to mis-diagnosis... btw i'm high as fuck so sorry this is long.