Difficulty breathing and dizziness after a hot chocolate!?!??

Hi ladies! Im 20+4 Weeks and everything has been going smoothly so far. But yesterday I indulged with a regular size hot cocoa as a treat for my long walk in the freezing cold. Not something I usually do, but I really craved it. But as soon as I finished it, I started to feel light-headed and had difficulty breathing as if my clothes were suddenly too tight and were compressing my chest. Whats up with that!??? Ok I might have drink it a bit fast because it was hot and I was cold, but still. It lasted about half an hour. Did something similar ever happened during pregnancy? What is that all about??