Wow man... its perfectly normal... and also very enjoyable, at least for me... i used to feel like that when i would be REALLY high, what were far more frequent when i was new to smoking... today i rarely feel it... Anyway, i would lay down in the ground, look at the sky, and would feel that i would fall to the sky... when there were clouds, the thing were FAR crazier... as the clouds looked like a ground far below, and i felt like i would fall there... it was trippy... and i loved it... so, my friend, enjoy it while you can... as i (and many other stoners also) would have to smoke a LOT for getting this feeling again...

PS. The best way for deal with it is just follow the flow... if you are feeling in a rollercoaster, go with it. If you feel youre falling, then fall. Let it go, dont fight, so it will be more enjoyable and less disturbing. :thumbsup::stoned: