Oh My god please don't do that to him. If you are really sure that u don't want to be with him, let him know. You don't have to be rude, just tell him u don't think its working out and you don't feel as close to him as u used too. Do not tell him that you found someone else. That is the worse thing you could do to him. If you are truly happy with this other guy and you are sure you want to be with him then be with him, not because you are not getting along with your boyfriend. The other guy could be temporary relief from what your going through at home. You really need to step out of the situation and reflect on what you would want someone to do for you in this situation. Don't do what men do everyday. They move to someone else because they think the grass is greener, its not. The grass turns brown every now and then. It may be brown now but there is a chance that it can be green again!