Whose last name should my son get? We aren't married!

Me and my boyfriend are 19 and pregnant. We love each other but don't have a perfect relationship. He would marry me in a heartbeat, but I'm not too comfortable w the thought of marriage at such a young age and w our relationship being as immature as it can be. I still want to be w him and raise our baby boy together, but I'm lost on the last name. Please give me thoughts and opinions!!!! Of course my family is fighting for our last name and his is fighting for theirs, but I feel like outsiders thoughts would help as well.