Can a boy the age of 18 or 19 go to jail of get in trouble for impregnating a girl the age of 15? What if they are having intercourse and she isn't pregnant? If the girls parents calls the police and reports this and the girl doesn't cooperate with the police and denies any claim of rape what will happen?

In terms of breaking the law, as long as the age difference between the two people is less than 4 years, intercourse between the two people is allowed. If the age difference is more than 4 years, the penalty is at least a $800 fine and 5-10 years in prison. It's usually pretty easy to prove that sexual intercourse has occurred with a female, as there's biological evidence up to three days after the last occurrence of intercourse, or if the girl is pregnant, so whether or not the girl cooperates with the police is a mute point. If the girl does become pregnant, and the age difference is less than 4 years, it is entirely her decision, legally speaking, to decide to keep the child, and if she does, the father would be responsible for child support for the next 18 years.