I'm going to leave my pregnant girlfriend
WOW, Why do you want to leave her?
I don't want her being a burden on me after having the a child.
It is normal to be concerned about having a baby.  It is wrong to abandon the responsibility of a child.   You could ruing the life of both the child and mother and miss out on being a father.
Anyway, I'm going to be a good father.
It is wrong to abandon the mother of your child. You will always have a bond with her because of your child.