i dont know if someone has brought this up already but...Did you switch strains that you were smoking? I've been smoking The Hog lately, and if i smoke too much (and by too much i mean 1/2 of 3/4s of a bong bowl) I get the same symptoms of you. Most of the time when I get super high I get the rollercoaster feeling, and panicky thing too. So maybe you just need to take it easy, or switch to a sativa for a little while or somehting like that.