It’s sad that the child will grow up without a father, but it’s sadder that you’ll have to lie to the child when it asks about him. In a normal sperm donation situation you wouldn’t know the father’s identity either so you wouldn’t have to lie, but this isn’t that.
Plus, y’know, the child will be a constant reminder of how you’re not with the man you want to be. That’ll doubtless come through as you raise it.
These aren’t happy feels.