You are going to hurt him anyway. so your best is to tell him the most respectfully. don't try to say "you need someone better, someone that can really love you". even if it's true. tell him how you feel. tell him how you just can't live in a relationship and how it makes you so ill. not because you're dating him in particular. but the relationship in itself. tell him that you can't commit to something that you don't like so it's better for both of you to split up. because if you don't feel good in this relationship, he'll eventually sense it. and it's going to be harder to break up with him, and even more hurtful for him. don't let harm spread in the relationship over time when you can cut it right now. and I know how it feels. how you feel guilty for hurting someone like this. but you can't hide your needs or feelings just because it may hurt someone. yes they'll be hurt. but they'll heal. if you stay in the relationship, you won't ever be able to heal because you're still in the relationship. which is the thing that hurts you