Baby's last name

Rachel
Okay so I found out a little over a week ago that I'm about 7 weeks pregnant. The baby's father for the first couple days was pretty excited, thought this would be a good thing for him, considering he's made some bad choices and the fact he saw the pregnancy coming. We're both 18 so the pregnancy wasn't planned. After a few days he decided this wasn't what he wanted and he up and left, his moms planning on talking some sense into him but I doubt he'll be sticking around whatsoever. So I guess my question is, would it be wrong to give our child my last name rather than his? Since he'll have very little involvement if any in his child's life.