What can I do if my sons dad doesnt care about him?

my son is 14 months and his real father barely ever sees him, maybe once a month if that and when he does see him its only for a few mins to a half hour. He always has excuses like he doesnt have transportation or money. My son calls my bf now dad I dont tell him too he just does hes 14 months. He is very attatched to him too. I feel bad that his real dad is not in his life but he never offers to help with anything can I rake him for full custody and do you you think i would be able to get full custody of him?