IMO, this sounds like a classic case of panic/anxiety disorder. And especially the fact that it happens during one routine or 'ritual', i.e. getting stoned.

usually when people have anxiety, there is a certain act or thing that will trigger an attack. in your case, it sounds like taking bong hits. then again, sometimes when i take big bong rips i find it hard to catch my breath. if this is happening you to, maybe your lack of ability to catch your breath after a big bong rip is triggering a panic/anxiety attack.

ps, get off of the klonopin asap. you have to ween yourself off, or you could have seizures from withdrawal. that drug is so barbaric. what it does is shuts off your gaba production, which is a substance that helps you process thoughts. basically it lobotomizes you for the day. if you end up taking it over a long period of time, youll be lucky to ever stop taking it due to dependence.