I need some advice on my boyfriends drug addiction

Marijuana is not an addictive drug. It sounds to me like he's experimenting more than anything. Instead of freaking out and thinking of him as an "out of control drug addict", which I doubt he is, why don't you talk to him about it. Pot can by psychologically addictive - to an extent - but unless he's smoking it all day every day and not leaving the house or doing anything else, it's not that serious. If he starts experimenting with things like coke or heroin, that's when you should be concerned. If you try to talk to him about it in an objective and rational manner and he's unresponsive or angry, perhaps it's time to move on.
I'm not a doctor or anything, so that's just my opinion. I used to smole pot all the time when I was around that age. It's been years now. It was just a phase and it veryu well may be just that for your boyfriend. Good luck. Hope that was some help.