ADR531

i use to smoke everyday for a few months or so, then i stopped for about 2weeks. my friend got about an 1/8 of dank so we rolled a fat joint and clam baked in his car. i took a few shotties and a lot of hits, i was really really ****ed up and when i got back inside i couldn't even walk around. i would lift my hand to get a drink and start blacking out, my whole vision went fuzzy and i knew i was ****ed up. my heart fel;t like it was going to pop right out. i was messed up for atleast 4hrs and i was completely wrecked. has this ever happened to anyone where u start to black out when ur moving around and really high? and could i have given myself a heartattack and is it risky to ever smoke this much? what exactly is the worst that can happen? thanks.