Do you mean only when you hit off a pipe or bong, or when you walk around too?

I don't have any extra difficulty breathing normally, but now it seems like it is more difficult to breathe in all of the smoke when I smoke. My bubbler is so awesome and I know it so well that I can burn maybe .7 grams in one hit, so it could just be that I am better at smoking now. Maybe you are that way too. It feels like my lungs have been filled with concrete when I do HUGE hits like that. It's how I imagine drowning would feel after the initial OH SHIT reaction. I don't think drowning would be terribly bad.