For starters I'm a health/ fitness nut 90% of the time, but my mate has a birthday party two nights ago and I got pretty drunk, the next morning I vomited up everything as excepted, all was good. The next morning I felt like I had a tight chest, I can breath normally but my breathes are really shallow, if I take a deep breath I feel a mild pain just under my sternum. Can someone please explain why I am having difficulties breathing? (Never experinced this before)