Coughing up blood is caused my internal damage which leads to internal bleeding. Call yo mother fucking docta right naow.
You are freaking out man. I bet you anything that your mouth was bleeding in some way. If you had been smoking cigs for a few decades then yes I would believe that was the problem.
last summer i was smoking pretty much the amount you do. one night i was smoking out of a bong and a few minutes after my last hit i noticed my throat hurting a LOT. it turns out i burned my throat because even though i was using a bong the smoke was way too hot. i wasnt coughing but i noticed my spit had blood in it. it was weird.