It could be the strain. I knew some people that wouldnt get high from a pure indica, would get ill if they smoked a pure sativa and found a 50/50 mix the best. I dont know if youve already done this, but next time you get a sack just try a few tokes first and see how it affects you. If youre not used to a sativa high, it can sometimes make people feel ill because the high is all in the head and not in the body. Different strokes for different folks.