Hi there ~
I understand your concerns. However it is not unusual to have stretch marks
from growth while cracks seem to be concerning. I believe you have reason to consult an adolescent medicine specialist or a qualified local doctor who can take a look at the "cracks" and make sure it is not any other infection of any sort. I believe you will heal over time and are able to become sexually active if you wait and take the advise of consulting a doctor.
I hope this helps. Take care and have a lovely day!