(all of the above-mentioned acknowledged)
if it is repeatable(sounds like it), try a couple safe experiments:
observe your breathing. i even forget to. yeah. increased co2 leads your body to "think its drowning". drowning causes anxiety.
try bringing wifey with you, for a change? see if that helps or hurts.
my un-pedigreed advice says you're straining & probably holding in "bad air" like the 19th century quackery.
i don't have a wifey to try this on, so let me know how it goes... (lol)
for a side tangent... the 1st thing that struck me about Subcool the Weednerd was his fucked up lungs & coughing & how i'm about 15 yrs behind him, if i keep at it.