If I choose to be child free by choice for medical reasons, am I better off alone so I don't hurt anyone?

No your not better off alone. He obviously loves you hes there for you and supports you. If you have discussed this and he agrees with you that's what matters, if someday you decide you want children there are plenty of alternatives. Having somebody to come home to that loves you and understands you is the best in the world. I'm sure he feels that way so it would be taking that away from him to, the love of his life. You also don't want to what if for the rest of your life and decide after its to late. I hope this helps