The one point I keyed on was he is your first relationship and you want him to be your last. From experience I can tell you that you need to get out there and experience more. You have no way of knowing if he is the right person for you if you have nothing to compare it to.

A first love is always going to be a special person and will always maintain a place in your heart so I can understand the reluctance to leave. He is the only (relationship) happiness you have ever experienced and you don't want to hurt him. However it is better to hurt him (and yourself) now before you make a commitment that you may regret down the road. Getting married and having kids requires a long and painful U-turn if you went in the wrong direction.

Besides if you explain to him that you need time to sort out your feelings for him, if he really does love you and want to be with you then he will be there when you are ready to come back.