I think it means to get out of breath, so it's similar to getting tired. I'm pretty sure it's a British usage.

I've never heard that expression before. Do you mean "being pooped"? "Pooped" means tired. For example: I'm pooped. I'm going to be pooped after working for 12 hours.

This one is funny too. What kind of things are you watching or what kind of people are you hanging out with? :) I think here you are referring to being "puffed up". Don't get all puffed up about it means don't get yourself into a tither, don't get yourself riled up, don't sweet it - calm down, relax, don't get angry or get upset. Chill brother!