People have all sorts of reactions to smoking weed, inlcuding fainting and dizziness, jitters and perspiration and agitation. Depends on the individual who's smoking, how he's feeling, and how the weed affects him. I'm sure it also depends a lot on the strain you're smoking and what its sativa vs indica content is.

Consider your response easily within the realm of normal from what I've read about responses to weed, albeit a strong enough response that it'd be wise to proceed cautiously the next time. You may find some interesting and reassuring info on one or both of these sites:
http://www.erowid.org/ (see Plants & Drugs/Cannabis)
http://www.norml.org/ (navigate to the Medical Use area)
birdgirl73 Reviewed by birdgirl73 on . Dizziness and feeling of fainting after smoking? Whats wrong with me? Well around 2 days ago I smoked a bit in the morning. Ive smoked marijuana around 11-12 times now so I know how to smoke it properly. But 2 days ago I mean wow. I was lying on my bed playing my XB360 and then I decided to get up and have a glass of water(I was starting to feel a buzz until then). Immediatly I became extremely dizzy. My heart was beating at a crazy speed and I was shaking and sweating. My whole vision became blurry and I was losing my balance and I was on the verge of fainting. Rating: 5