Wtf? You're 19, honey ~ run while you still have flat abs and emotional ability to get over the guy. You're WAY too young to have to deal with issues like this guy apparently has. Not that it can't be overcome like the Anonymous comment above indicates ~ but, seriously, that type of recovery is rare and extremely hard to come by. Your man NEEDS to want the change - for him, not you. You're just a baby, sweetie ~ and I'm living proof that lost souls like your boyfriend just stain your romantic partnership experiences going forward. While it's admirable that you'd like to 'save' the relationship and 'save' him ~ honestly, it's a wasted effort on your part when you consider YOUR age. Please, tell him that you care deeply and want the best for him, give him an armload of literature on the subject and phone numbers for the nearest professional and then let him know you are just plain, ill-equipped with his problems and walk away with your head held high and your self-esteem still in tact. There's absolutely no harm in saving yourself first and you, my friend, are going out with a problematic fellow - trust me, it'll get worse before it gets better.
Good luck, baby - you're gonna need it.