Dad I miss you

My story is complicated. I’m the end my son admits of missing his father. This is something I can’t control. He hasn’t seen his dad for any holiday or any day he is with his grandmother.. meaning when my son is being which by his mother. I can’t tell anyone to be a father again even if there’s a newborn on the way. I didn’t know what to say to my little toddler. Words just ran out.. it went from “ we don’t need him” “ if he misses you he will come to you” to being speechless.. since my pregnancy leave I’ve been spending so much time with him. And he thinks life isn’t fair cause he doesn’t have a whole family. I’d asked him if he wanted me to find him a new father to look up. And my son says why can’t you fix my own dad. The one that looks like me.. the one who use to show me love tell me to be brave. The one who use to love you as much as I did. Being a single mother was hard at first. But hearing stuff like this.. I really don’t know what to say or do.. I never want my son to feel heartbroken but he does.. need some advice