Last name

So I'm feeling strongly that I want to give this baby my last name because the baby daddy and me are not together. Now this is not a decision against him or because I am mad or any other negative towards him (other than my fear of him leaving) but mostly because I feel like I really want the same last name as my baby. I am giving this baby one of his middle names so he will still have a connection to him but I am torn on the issue of the last name. The dad has already talked about moving out of state, gave up his spot at my next ultrasound to my mother, and done a couple other things indicating he won't be involved. A part of me is scared to name this child after someone who might not be in his life and this kid will grow up with no connection to his last name. Also as the main parent I would have to carry a birth certificate with me if we fly or go out of the country because I do not have the same last name as him which seems like a hassle. I also am carrying this baby and going to all of the appointments by myself and the dad has already told me he isn't sure he'll still be in the state at the birth so I might do that alone. I guess my question is do you think my son would grow up to be upset with the fact he doesn't have his dads last name? Or is it wrong to "take this away" (his words) from the baby daddy? I am just so conflicted because I know either way I will be connected to my son but what if the last name is the only way he will feel connected and me choosing mine over his pushes him further out of the picture.