man u just need to take it easy. ive been smoking for a really long time ant the only time ive thrown up while smoking is once when i took a really huge bong rip. maybe youre problem is that youre inhaling too much smoke and your lungs arent used to it. If i were u i would just keep a drink handy while ur smokin and if u feel like ur gonna yak just take a drink and try not to think about it