Im confused and want help.

Ive been doing nangs for about two years now.. ive done them sober, stoned, on lsd, on MDMA, and on all three at the same time and have loved them the whole way through, they're a nice little addition to a good night in my opinion.. but recently ive started having 'unconscious seiziures' after i stop using the balloon. im fine huffing the balloon and everything and the nang is fine, but when i stop huffing something happens and it causes me to lose conciousness, get up and start swinging my arms vigorously around the room and then i sit back down. In my mind, i experience my vision completely whirlpooling in four different sectors but with enough details that I can barely see whats going on infront of me (keep in mind aparently my eyes are closed at this stage) and I have a fear that pops up every single time it happens that im going to be stuck like that. after a few seconds i regain conciousness and i look around at usually my girlfriend holding my arms down and yelling at me (i havent done them too much since this started happening as im confused as fuck) and yet in my head, the whole time i have sat in the same position relaxed as ever. Im really worried that i have something wrong with me and just want to know if anyone could shed some light, i understand some people just cant handle nangs but i definitely used to, and i feel like i do now but my body just doesnt seem to do it