Pregnant girlfriend?

i need some help im 17 and will be 18 the 29th of this month my g/f is 15 and we just found out she is 7 weeks pregnant her dad is a trucker and she lives with her gma she was mad but got over it her dad on the other hand is being childish he wont take my calls and just picks up the phone and beeps at me he says he disowns her we want to get married but he wont sign but he says she can move in with me im confused what do i do????i work construction and out of school i make good money but im in winter layoff so im working at goodys i can take care of us i know what its like not to have a dad and i wanna be there for my child.... if she does move in with me will i get in trouble???? is there really a law that says that u cant get in trouble for statitory unless she is 4 years to the day younger than me if so when im 18 we can still be together without being married......