Need ADVICE!!!!

There is no real way to break the news to him without hurting him to some extent. Think about how you can minimize the hurt, the way to do that is to be honest with him about how you feel and explain it clearly with your reasons.

The sooner you are able to let him know, the smaller the amount of pain that will be inflicted. If you leave it too long, it will hurt even more.

Good luck, remember to be honest with him.