I just did 10 long puffs (the method described above), and I had troubles breathing, -take a deep breath, then take a breath on top of that - it felt like that, it quickly (20 seonds) went away though, and now Im breathing normal again. The reason I tried was because I wasnt getting that same light headed feeling. I have only had 5 hours sleep though. I use the light headed feeling as an indicator of thats enough, so I guess there is a limit. I have reason to believe its the nicotine since I have vaped a lot (constantly) before using no nicotine (just trying an ecig) and it never happened. TL;DR It's all fine, just if you feel like you can't breathe normally, tell someone (in case it doesn't go away), and just see if it goes away quickly, it did for me.