I will tell you one thing, being with someone for a long time and trying to build up their confidence or help them through their troubles is not the way to go, though it is very thoughtful.

I was with a girl for two years and during that process the only thing that happened was I raised her self confidence and she lowered mine. So it's not a good thing for you. Now one thing you have to realize is to not be selfish in this situation. After all, this is your decision and you have to play it out. You can't just sit there and try to make him dislike you enough to break up with you because that is just wrong and is very selfish. It's your decision and although it is probably the right decision, don't back down from it. When you feel it's time you'll know and when that time comes tell him peacefully and calmly and tell him face to face. Although you should let him know that even though it's not working at this time it doesn't mean it never will. He may get better with his problems and you better with yours and some time it might actually work out. Right now you just need to have a break and some time away from him, get you some therapy and go from there. Best of luck.