Why cant i get high anymore?

i used to smoke allllll the time for like 2 years and then one time i like "overdosed" and had to go to the hospital. i was throwing up everything and couldnt breathe and my heart was beating twice as fast as it should and i got busted. then i tried it a few months later and the same thing happened. so i just dont do it anymore. i take strattera, which is a narcotic for ADHD, every morning. i pretty much only smoked nugg and i miss doing it sooooooo much and want to do it still. WHY?!?!