Hello,what mode of delivery she had before?(cesarean or normal). If she had any complications in her first delivery or after that(like infections). If so then there may be adhesions in uterus preventing her to get pregnant. if she is not getting pregnant again then she need to undergo some tests visit a fertility centre near you or another gynecologist she will do the tests. While they may help to get her pregnant but baby boy was not guarantee and can not be done on sure.