Is it obligatory to apologize to a former girlfriend who was wronged because she was left, and is that a reason for not conceiving?

Leaving a girl after intending to marry her is not an injustice to her, especially if the rejection came from her father. If you did wrong her, then you must repent and seek her forgiveness, provided that no greater harm results from doing so. Deprivation of offspring may be a trial, not a punishment, so face that with patience, striving, supplication, and seeking forgiveness.